[DarkMode] remove enableLegacyPatching option

The option was only allowed to be set to `false`, so it's not been
used at all, so now we can remove it, given that we've had the dark
mode legacy patching disabled without any major bugs in the past few
weeks.

Bug: chromium:1152736
Change-Id: I1e794d75f9c354a0d16b1b3975f7ebdf82b3448b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2988303
Commit-Queue: Jack Franklin <[email protected]>
Reviewed-by: Paul Lewis <[email protected]>
diff --git a/front_end/entrypoints/inspector_main/InspectorMain.ts b/front_end/entrypoints/inspector_main/InspectorMain.ts
index 77d0e7b..7fea978 100644
--- a/front_end/entrypoints/inspector_main/InspectorMain.ts
+++ b/front_end/entrypoints/inspector_main/InspectorMain.ts
@@ -146,8 +146,7 @@
   private constructor() {
     const element = document.createElement('div');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        element,
-        {cssFile: 'entrypoints/inspector_main/nodeIcon.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        element, {cssFile: 'entrypoints/inspector_main/nodeIcon.css', delegatesFocus: undefined});
     this._element = shadowRoot.createChild('div', 'node-icon');
     element.addEventListener(
         'click', () => Host.InspectorFrontendHost.InspectorFrontendHostInstance.openNodeFrontend(), false);
diff --git a/front_end/entrypoints/inspector_main/RenderingOptions.ts b/front_end/entrypoints/inspector_main/RenderingOptions.ts
index 2058498..637b68e 100644
--- a/front_end/entrypoints/inspector_main/RenderingOptions.ts
+++ b/front_end/entrypoints/inspector_main/RenderingOptions.ts
@@ -210,7 +210,7 @@
 export class RenderingOptionsView extends UI.Widget.VBox {
   private constructor() {
     super(true);
-    this.registerRequiredCSS('entrypoints/inspector_main/renderingOptions.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('entrypoints/inspector_main/renderingOptions.css');
 
     this._appendCheckbox(
         i18nString(UIStrings.paintFlashing), i18nString(UIStrings.highlightsAreasOfThePageGreen),
diff --git a/front_end/entrypoints/node_main/NodeConnectionsPanel.ts b/front_end/entrypoints/node_main/NodeConnectionsPanel.ts
index f6f4bd2..6564985 100644
--- a/front_end/entrypoints/node_main/NodeConnectionsPanel.ts
+++ b/front_end/entrypoints/node_main/NodeConnectionsPanel.ts
@@ -43,7 +43,7 @@
   _networkDiscoveryView: NodeConnectionsView;
   private constructor() {
     super('node-connection');
-    this.registerRequiredCSS('entrypoints/node_main/nodeConnectionsPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('entrypoints/node_main/nodeConnectionsPanel.css');
     this.contentElement.classList.add('node-panel');
 
     const container = this.contentElement.createChild('div', 'node-panel-center');
@@ -104,7 +104,7 @@
         i18n.i18n.getFormatLocalizedString(str_, UIStrings.specifyNetworkEndpointAnd, {PH1: documentationLink}));
 
     this._list = new UI.ListWidget.ListWidget(this);
-    this._list.registerRequiredCSS('entrypoints/node_main/nodeConnectionsPanel.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('entrypoints/node_main/nodeConnectionsPanel.css');
     this._list.element.classList.add('network-discovery-list');
     const placeholder = document.createElement('div');
     placeholder.classList.add('network-discovery-list-empty');
diff --git a/front_end/models/persistence/EditFileSystemView.ts b/front_end/models/persistence/EditFileSystemView.ts
index 0fab8e1..69a334e 100644
--- a/front_end/models/persistence/EditFileSystemView.ts
+++ b/front_end/models/persistence/EditFileSystemView.ts
@@ -81,7 +81,7 @@
   _excludedFolderEditor?: UI.ListWidget.Editor<string>;
   constructor(fileSystemPath: string) {
     super(true);
-    this.registerRequiredCSS('models/persistence/editFileSystemView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('models/persistence/editFileSystemView.css');
     this._fileSystemPath = fileSystemPath;
 
     this._excludedFolders = [];
@@ -98,8 +98,7 @@
         i18nString(UIStrings.add), this._addExcludedFolderButtonClicked.bind(this), 'add-button'));
     this._excludedFoldersList = new UI.ListWidget.ListWidget(this);
     this._excludedFoldersList.element.classList.add('file-system-list');
-    this._excludedFoldersList.registerRequiredCSS(
-        'models/persistence/editFileSystemView.css', {enableLegacyPatching: false});
+    this._excludedFoldersList.registerRequiredCSS('models/persistence/editFileSystemView.css');
     const excludedFoldersPlaceholder = document.createElement('div');
     excludedFoldersPlaceholder.classList.add('file-system-list-empty');
     excludedFoldersPlaceholder.textContent = i18nString(UIStrings.none);
diff --git a/front_end/models/persistence/WorkspaceSettingsTab.ts b/front_end/models/persistence/WorkspaceSettingsTab.ts
index 0bfb41b..6a2846b 100644
--- a/front_end/models/persistence/WorkspaceSettingsTab.ts
+++ b/front_end/models/persistence/WorkspaceSettingsTab.ts
@@ -48,7 +48,7 @@
   _mappingViewByPath: Map<string, EditFileSystemView>;
   private constructor() {
     super();
-    this.registerRequiredCSS('models/persistence/workspaceSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('models/persistence/workspaceSettingsTab.css');
 
     const header = this.element.createChild('header');
     UI.UIUtils.createTextChild(header.createChild('h1'), i18nString(UIStrings.workspace));
diff --git a/front_end/panels/accessibility/AXBreadcrumbsPane.ts b/front_end/panels/accessibility/AXBreadcrumbsPane.ts
index 7ec09f4..5700292 100644
--- a/front_end/panels/accessibility/AXBreadcrumbsPane.ts
+++ b/front_end/panels/accessibility/AXBreadcrumbsPane.ts
@@ -60,7 +60,7 @@
     this._rootElement.addEventListener('click', this._onClick.bind(this), false);
     this._rootElement.addEventListener('contextmenu', this._contextMenuEventFired.bind(this), false);
     this._rootElement.addEventListener('focusout', this._onFocusOut.bind(this), false);
-    this.registerRequiredCSS('panels/accessibility/axBreadcrumbs.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/accessibility/axBreadcrumbs.css');
   }
 
   focus(): void {
diff --git a/front_end/panels/accessibility/AccessibilityNodeView.ts b/front_end/panels/accessibility/AccessibilityNodeView.ts
index f2a8c39..131177a 100644
--- a/front_end/panels/accessibility/AccessibilityNodeView.ts
+++ b/front_end/panels/accessibility/AccessibilityNodeView.ts
@@ -133,7 +133,7 @@
     this._ignoredReasonsTree = this.createTreeOutline();
 
     this.element.classList.add('accessibility-computed');
-    this.registerRequiredCSS('panels/accessibility/accessibilityNode.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/accessibility/accessibilityNode.css');
     this._treeOutline.setFocusable(true);
   }
 
diff --git a/front_end/panels/accessibility/AccessibilitySubPane.ts b/front_end/panels/accessibility/AccessibilitySubPane.ts
index 20ffcc6..3ee2d2c 100644
--- a/front_end/panels/accessibility/AccessibilitySubPane.ts
+++ b/front_end/panels/accessibility/AccessibilitySubPane.ts
@@ -14,7 +14,7 @@
     super(name);
 
     this._axNode = null;
-    this.registerRequiredCSS('panels/accessibility/accessibilityProperties.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/accessibility/accessibilityProperties.css');
   }
 
   setAXNode(_axNode: SDK.AccessibilityModel.AccessibilityNode|null): void {
@@ -37,9 +37,9 @@
 
   createTreeOutline(): UI.TreeOutline.TreeOutline {
     const treeOutline = new UI.TreeOutline.TreeOutlineInShadow();
-    treeOutline.registerRequiredCSS('panels/accessibility/accessibilityNode.css', {enableLegacyPatching: false});
-    treeOutline.registerRequiredCSS('panels/accessibility/accessibilityProperties.css', {enableLegacyPatching: false});
-    treeOutline.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
+    treeOutline.registerRequiredCSS('panels/accessibility/accessibilityNode.css');
+    treeOutline.registerRequiredCSS('panels/accessibility/accessibilityProperties.css');
+    treeOutline.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
 
     treeOutline.element.classList.add('hidden');
     treeOutline.hideOverflow();
diff --git a/front_end/panels/animation/AnimationScreenshotPopover.ts b/front_end/panels/animation/AnimationScreenshotPopover.ts
index a0f53e8..5725cf3 100644
--- a/front_end/panels/animation/AnimationScreenshotPopover.ts
+++ b/front_end/panels/animation/AnimationScreenshotPopover.ts
@@ -16,7 +16,7 @@
   constructor(images: HTMLImageElement[]) {
     super(true);
     console.assert(images.length > 0);
-    this.registerRequiredCSS('panels/animation/animationScreenshotPopover.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/animation/animationScreenshotPopover.css');
     this.contentElement.classList.add('animation-screenshot-popover');
     this._frames = images;
     for (const image of images) {
diff --git a/front_end/panels/animation/AnimationTimeline.ts b/front_end/panels/animation/AnimationTimeline.ts
index b237cb4..19e1a73 100644
--- a/front_end/panels/animation/AnimationTimeline.ts
+++ b/front_end/panels/animation/AnimationTimeline.ts
@@ -124,7 +124,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/animation/animationTimeline.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/animation/animationTimeline.css');
     this.element.classList.add('animations-timeline');
 
     this._gridWrapper = this.contentElement.createChild('div', 'grid-overflow-wrapper');
diff --git a/front_end/panels/application/AppManifestView.ts b/front_end/panels/application/AppManifestView.ts
index 7555da6..d52df4e 100644
--- a/front_end/panels/application/AppManifestView.ts
+++ b/front_end/panels/application/AppManifestView.ts
@@ -351,7 +351,7 @@
   _serviceWorkerManager?: SDK.ServiceWorkerManager.ServiceWorkerManager|null;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/application/appManifestView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/appManifestView.css');
     this.contentElement.classList.add('manifest-container');
 
     Common.Settings.Settings.instance()
@@ -366,7 +366,7 @@
 
     // TODO(crbug.com/1156978): Replace UI.ReportView.ReportView with ReportView.ts web component.
     this._reportView = new UI.ReportView.ReportView(i18nString(UIStrings.appManifest));
-    this._reportView.registerRequiredCSS('panels/application/appManifestView.css', {enableLegacyPatching: false});
+    this._reportView.registerRequiredCSS('panels/application/appManifestView.css');
     this._reportView.element.classList.add('manifest-view-header');
     this._reportView.show(this.contentElement);
     this._reportView.hideWidget();
diff --git a/front_end/panels/application/ApplicationPanelSidebar.ts b/front_end/panels/application/ApplicationPanelSidebar.ts
index b9ab486..c415dc4 100644
--- a/front_end/panels/application/ApplicationPanelSidebar.ts
+++ b/front_end/panels/application/ApplicationPanelSidebar.ts
@@ -226,7 +226,7 @@
 
     this._sidebarTree = new UI.TreeOutline.TreeOutlineInShadow();
     this._sidebarTree.element.classList.add('resources-sidebar');
-    this._sidebarTree.registerRequiredCSS('panels/application/resourcesSidebar.css', {enableLegacyPatching: false});
+    this._sidebarTree.registerRequiredCSS('panels/application/resourcesSidebar.css');
     this._sidebarTree.element.classList.add('filter-all');
     // Listener needs to have been set up before the elements are added
     this._sidebarTree.addEventListener(UI.TreeOutline.Events.ElementAttached, this._treeElementAdded, this);
diff --git a/front_end/panels/application/BackgroundServiceView.ts b/front_end/panels/application/BackgroundServiceView.ts
index 45ccd0a..e36ec4d 100644
--- a/front_end/panels/application/BackgroundServiceView.ts
+++ b/front_end/panels/application/BackgroundServiceView.ts
@@ -157,8 +157,8 @@
 
   constructor(serviceName: Protocol.BackgroundService.ServiceName, model: BackgroundServiceModel) {
     super(true);
-    this.registerRequiredCSS('panels/application/backgroundServiceView.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('ui/legacy/emptyWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/backgroundServiceView.css');
+    this.registerRequiredCSS('ui/legacy/emptyWidget.css');
 
     this._serviceName = serviceName;
 
diff --git a/front_end/panels/application/CookieItemsView.ts b/front_end/panels/application/CookieItemsView.ts
index 51b48bb..fa776a9 100644
--- a/front_end/panels/application/CookieItemsView.ts
+++ b/front_end/panels/application/CookieItemsView.ts
@@ -173,7 +173,7 @@
   constructor(model: SDK.CookieModel.CookieModel, cookieDomain: string) {
     super(i18nString(UIStrings.cookies), 'cookiesPanel');
 
-    this.registerRequiredCSS('panels/application/cookieItemsView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/cookieItemsView.css');
     this.element.classList.add('storage-view');
 
     this._model = model;
diff --git a/front_end/panels/application/IndexedDBViews.ts b/front_end/panels/application/IndexedDBViews.ts
index 6768ecd..9e9e285 100644
--- a/front_end/panels/application/IndexedDBViews.ts
+++ b/front_end/panels/application/IndexedDBViews.ts
@@ -161,13 +161,13 @@
     this._model = model;
     const databaseName = database ? database.databaseId.name : i18nString(UIStrings.loading);
 
-    this.registerRequiredCSS('panels/application/indexedDBViews.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/indexedDBViews.css');
     this.contentElement.classList.add('indexed-db-container');
 
     // TODO(crbug.com/1156978): Replace UI.ReportView.ReportView with ReportView.ts web component.
     this._reportView = new UI.ReportView.ReportView(databaseName);
     this._reportView.show(this.contentElement);
-    this._reportView.registerRequiredCSS('panels/application/indexedDBViews.css', {enableLegacyPatching: false});
+    this._reportView.registerRequiredCSS('panels/application/indexedDBViews.css');
     this._reportView.element.classList.add('indexed-db-header');
 
     const bodySection = this._reportView.appendSection('');
@@ -253,7 +253,7 @@
       model: IndexedDBModel, databaseId: DatabaseId, objectStore: ObjectStore, index: Index|null,
       refreshObjectStoreCallback: () => void) {
     super(i18nString(UIStrings.idb));
-    this.registerRequiredCSS('panels/application/indexedDBViews.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/indexedDBViews.css');
 
     this._model = model;
     this._databaseId = databaseId;
diff --git a/front_end/panels/application/OpenedWindowDetailsView.ts b/front_end/panels/application/OpenedWindowDetailsView.ts
index 6133bfe..d6703cd 100644
--- a/front_end/panels/application/OpenedWindowDetailsView.ts
+++ b/front_end/panels/application/OpenedWindowDetailsView.ts
@@ -158,12 +158,11 @@
     super();
     this._targetInfo = targetInfo;
     this._isWindowClosed = isWindowClosed;
-    this.registerRequiredCSS('panels/application/frameDetailsReportView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/frameDetailsReportView.css');
     this.contentElement.classList.add('frame-details-container');
     // TODO(crbug.com/1156978): Replace UI.ReportView.ReportView with ReportView.ts web component.
     this._reportView = new UI.ReportView.ReportView(this.buildTitle());
-    this._reportView.registerRequiredCSS(
-        'panels/application/frameDetailsReportView.css', {enableLegacyPatching: false});
+    this._reportView.registerRequiredCSS('panels/application/frameDetailsReportView.css');
     this._reportView.show(this.contentElement);
     this._reportView.element.classList.add('frame-details-report-container');
 
@@ -226,13 +225,12 @@
   constructor(targetInfo: Protocol.Target.TargetInfo) {
     super();
     this._targetInfo = targetInfo;
-    this.registerRequiredCSS('panels/application/frameDetailsReportView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/frameDetailsReportView.css');
     this.contentElement.classList.add('frame-details-container');
     // TODO(crbug.com/1156978): Replace UI.ReportView.ReportView with ReportView.ts web component.
     this._reportView =
         new UI.ReportView.ReportView(this._targetInfo.title || this._targetInfo.url || i18nString(UIStrings.worker));
-    this._reportView.registerRequiredCSS(
-        'panels/application/frameDetailsReportView.css', {enableLegacyPatching: false});
+    this._reportView.registerRequiredCSS('panels/application/frameDetailsReportView.css');
     this._reportView.show(this.contentElement);
     this._reportView.element.classList.add('frame-details-report-container');
 
diff --git a/front_end/panels/application/ResourcesPanel.ts b/front_end/panels/application/ResourcesPanel.ts
index 05f48b4..699ca6e 100644
--- a/front_end/panels/application/ResourcesPanel.ts
+++ b/front_end/panels/application/ResourcesPanel.ts
@@ -34,7 +34,7 @@
 
   private constructor() {
     super('resources');
-    this.registerRequiredCSS('panels/application/resourcesPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/resourcesPanel.css');
 
     this._resourcesLastSelectedItemSetting =
         Common.Settings.Settings.instance().createSetting('resourcesLastSelectedElementPath', []);
diff --git a/front_end/panels/application/ServiceWorkerCacheViews.ts b/front_end/panels/application/ServiceWorkerCacheViews.ts
index 366c822..fde760a 100644
--- a/front_end/panels/application/ServiceWorkerCacheViews.ts
+++ b/front_end/panels/application/ServiceWorkerCacheViews.ts
@@ -91,7 +91,7 @@
   }>|null;
   constructor(model: SDK.ServiceWorkerCacheModel.ServiceWorkerCacheModel, cache: SDK.ServiceWorkerCacheModel.Cache) {
     super(i18nString(UIStrings.cache));
-    this.registerRequiredCSS('panels/application/serviceWorkerCacheViews.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/serviceWorkerCacheViews.css');
 
     this._model = model;
     this._entriesForTest = null;
diff --git a/front_end/panels/application/ServiceWorkersView.ts b/front_end/panels/application/ServiceWorkersView.ts
index bbf91cd..42a853c 100644
--- a/front_end/panels/application/ServiceWorkersView.ts
+++ b/front_end/panels/application/ServiceWorkersView.ts
@@ -187,7 +187,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/application/serviceWorkersView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/serviceWorkersView.css');
 
     // TODO(crbug.com/1156978): Replace UI.ReportView.ReportView with ReportView.ts web component.
     this._currentWorkersView = new UI.ReportView.ReportView(i18n.i18n.lockedString('Service Workers'));
@@ -814,9 +814,9 @@
   }
 
   _wrapWidget(container: Element): Element {
-    const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        container, {cssFile: undefined, enableLegacyPatching: false, delegatesFocus: undefined});
-    UI.Utils.appendStyle(shadowRoot, 'panels/application/serviceWorkersView.css', {enableLegacyPatching: false});
+    const shadowRoot =
+        UI.Utils.createShadowRootWithCoreStyles(container, {cssFile: undefined, delegatesFocus: undefined});
+    UI.Utils.appendStyle(shadowRoot, 'panels/application/serviceWorkersView.css');
     const contentElement = document.createElement('div');
     shadowRoot.appendChild(contentElement);
     return contentElement;
diff --git a/front_end/panels/application/StorageView.ts b/front_end/panels/application/StorageView.ts
index 438f94a..c83a6fd 100644
--- a/front_end/panels/application/StorageView.ts
+++ b/front_end/panels/application/StorageView.ts
@@ -160,7 +160,7 @@
 
   constructor() {
     super(true, 1000);
-    this.registerRequiredCSS('panels/application/storageView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/application/storageView.css');
     this.contentElement.classList.add('clear-storage-container');
     this.pieColors = new Map([
       [Protocol.Storage.StorageType.Appcache, 'rgb(110, 161, 226)'],        // blue
@@ -174,7 +174,7 @@
 
     // TODO(crbug.com/1156978): Replace UI.ReportView.ReportView with ReportView.ts web component.
     this.reportView = new UI.ReportView.ReportView(i18nString(UIStrings.storageTitle));
-    this.reportView.registerRequiredCSS('panels/application/storageView.css', {enableLegacyPatching: false});
+    this.reportView.registerRequiredCSS('panels/application/storageView.css');
     this.reportView.element.classList.add('clear-storage-header');
     this.reportView.show(this.contentElement);
     /** @type {?SDK.Target.Target} */
diff --git a/front_end/panels/browser_debugger/CategorizedBreakpointsSidebarPane.ts b/front_end/panels/browser_debugger/CategorizedBreakpointsSidebarPane.ts
index 4a85774..66e187b 100644
--- a/front_end/panels/browser_debugger/CategorizedBreakpointsSidebarPane.ts
+++ b/front_end/panels/browser_debugger/CategorizedBreakpointsSidebarPane.ts
@@ -32,8 +32,7 @@
       detailsPausedReason: Protocol.Debugger.PausedEventReason) {
     super(true);
     this._categoriesTreeOutline = new UI.TreeOutline.TreeOutlineInShadow();
-    this._categoriesTreeOutline.registerRequiredCSS(
-        'panels/browser_debugger/categorizedBreakpointsSidebarPane.css', {enableLegacyPatching: false});
+    this._categoriesTreeOutline.registerRequiredCSS('panels/browser_debugger/categorizedBreakpointsSidebarPane.css');
     this._categoriesTreeOutline.setShowSelectionOnKeyboardFocus(/* show */ true);
     this.contentElement.appendChild(this._categoriesTreeOutline.element);
     this._viewId = viewId;
diff --git a/front_end/panels/browser_debugger/DOMBreakpointsSidebarPane.ts b/front_end/panels/browser_debugger/DOMBreakpointsSidebarPane.ts
index c7defa3..9eb2185 100644
--- a/front_end/panels/browser_debugger/DOMBreakpointsSidebarPane.ts
+++ b/front_end/panels/browser_debugger/DOMBreakpointsSidebarPane.ts
@@ -126,7 +126,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/browser_debugger/domBreakpointsSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/browser_debugger/domBreakpointsSidebarPane.css');
 
     this.elementToCheckboxes = new WeakMap();
 
diff --git a/front_end/panels/browser_debugger/XHRBreakpointsSidebarPane.ts b/front_end/panels/browser_debugger/XHRBreakpointsSidebarPane.ts
index ab3f65f..85a4c14 100644
--- a/front_end/panels/browser_debugger/XHRBreakpointsSidebarPane.ts
+++ b/front_end/panels/browser_debugger/XHRBreakpointsSidebarPane.ts
@@ -78,7 +78,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/browser_debugger/xhrBreakpointsSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/browser_debugger/xhrBreakpointsSidebarPane.css');
 
     this._breakpoints = new UI.ListModel.ListModel();
     this._list = new UI.ListControl.ListControl(this._breakpoints, this, UI.ListControl.ListMode.NonViewport);
diff --git a/front_end/panels/changes/ChangesSidebar.ts b/front_end/panels/changes/ChangesSidebar.ts
index 62495d3..8c4587d 100644
--- a/front_end/panels/changes/ChangesSidebar.ts
+++ b/front_end/panels/changes/ChangesSidebar.ts
@@ -29,7 +29,7 @@
     super();
     this._treeoutline = new UI.TreeOutline.TreeOutlineInShadow();
     this._treeoutline.setFocusable(false);
-    this._treeoutline.registerRequiredCSS('panels/changes/changesSidebar.css', {enableLegacyPatching: false});
+    this._treeoutline.registerRequiredCSS('panels/changes/changesSidebar.css');
     this._treeoutline.setComparator((a, b) => Platform.StringUtilities.compare(a.titleAsText(), b.titleAsText()));
     this._treeoutline.addEventListener(UI.TreeOutline.Events.ElementSelected, this._selectionChanged, this);
     UI.ARIAUtils.markAsTablist(this._treeoutline.contentElement);
diff --git a/front_end/panels/changes/ChangesView.ts b/front_end/panels/changes/ChangesView.ts
index 4cf00df..0d25e42 100644
--- a/front_end/panels/changes/ChangesView.ts
+++ b/front_end/panels/changes/ChangesView.ts
@@ -67,7 +67,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/changes/changesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/changes/changesView.css');
     const splitWidget = new UI.SplitWidget.SplitWidget(true /* vertical */, false /* sidebar on left */);
     const mainWidget = new UI.Widget.Widget();
     splitWidget.setMainWidget(mainWidget);
diff --git a/front_end/panels/console/ConsoleContextSelector.ts b/front_end/panels/console/ConsoleContextSelector.ts
index 361b463..89d25a4 100644
--- a/front_end/panels/console/ConsoleContextSelector.ts
+++ b/front_end/panels/console/ConsoleContextSelector.ts
@@ -206,8 +206,7 @@
   createElementForItem(item: SDK.RuntimeModel.ExecutionContext): Element {
     const element = document.createElement('div');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        element,
-        {cssFile: 'panels/console/consoleContextSelector.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        element, {cssFile: 'panels/console/consoleContextSelector.css', delegatesFocus: undefined});
     const title = shadowRoot.createChild('div', 'title');
     UI.UIUtils.createTextChild(title, Platform.StringUtilities.trimEndWithMaxLength(this.titleFor(item), 100));
     const subTitle = shadowRoot.createChild('div', 'subtitle');
diff --git a/front_end/panels/coverage/CoverageListView.ts b/front_end/panels/coverage/CoverageListView.ts
index 1100987..388e2c7 100644
--- a/front_end/panels/coverage/CoverageListView.ts
+++ b/front_end/panels/coverage/CoverageListView.ts
@@ -142,7 +142,7 @@
     this._nodeForCoverageInfo = new Map();
     this._isVisibleFilter = isVisibleFilter;
     this._highlightRegExp = null;
-    this.registerRequiredCSS('panels/coverage/coverageListView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/coverage/coverageListView.css');
     const columns: DataGrid.DataGrid.ColumnDescriptor[] = [
       {id: 'url', title: i18nString(UIStrings.url), width: '250px', fixedWidth: false, sortable: true},
       {id: 'type', title: i18nString(UIStrings.type), width: '45px', fixedWidth: true, sortable: true},
diff --git a/front_end/panels/coverage/CoverageView.ts b/front_end/panels/coverage/CoverageView.ts
index 0c9d2d1..0f8c214 100644
--- a/front_end/panels/coverage/CoverageView.ts
+++ b/front_end/panels/coverage/CoverageView.ts
@@ -131,7 +131,7 @@
     this._decorationManager = null;
     this._resourceTreeModel = null;
 
-    this.registerRequiredCSS('panels/coverage/coverageView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/coverage/coverageView.css');
 
     const toolbarContainer = this.contentElement.createChild('div', 'coverage-toolbar-container');
     const toolbar = new UI.Toolbar.Toolbar('coverage-toolbar', toolbarContainer);
diff --git a/front_end/panels/css_overview/CSSOverviewCompletedView.ts b/front_end/panels/css_overview/CSSOverviewCompletedView.ts
index 396ea0b..54389d7 100644
--- a/front_end/panels/css_overview/CSSOverviewCompletedView.ts
+++ b/front_end/panels/css_overview/CSSOverviewCompletedView.ts
@@ -236,7 +236,7 @@
 
   constructor(controller: OverviewController, target: SDK.Target.Target) {
     super('css_overview_completed_view');
-    this.registerRequiredCSS('panels/css_overview/cssOverviewCompletedView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/css_overview/cssOverviewCompletedView.css');
 
     this._controller = controller;
     this._formatter = new Intl.NumberFormat('en-US');
@@ -253,8 +253,7 @@
     });
 
     // Dupe the styles into the main container because of the shadow root will prevent outer styles.
-    this._mainContainer.registerRequiredCSS(
-        'panels/css_overview/cssOverviewCompletedView.css', {enableLegacyPatching: false});
+    this._mainContainer.registerRequiredCSS('panels/css_overview/cssOverviewCompletedView.css');
 
     this._mainContainer.setMainWidget(this._resultsContainer);
     this._mainContainer.setSidebarWidget(this._elementContainer);
diff --git a/front_end/panels/css_overview/CSSOverviewPanel.ts b/front_end/panels/css_overview/CSSOverviewPanel.ts
index f97b373..3d544e8 100644
--- a/front_end/panels/css_overview/CSSOverviewPanel.ts
+++ b/front_end/panels/css_overview/CSSOverviewPanel.ts
@@ -42,7 +42,7 @@
 
   private constructor() {
     super('css_overview');
-    this.registerRequiredCSS('panels/css_overview/cssOverview.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/css_overview/cssOverview.css');
     this.element.classList.add('css-overview-panel');
 
     const [model] = SDK.TargetManager.TargetManager.instance().models(CSSOverviewModel);
diff --git a/front_end/panels/css_overview/CSSOverviewProcessingView.ts b/front_end/panels/css_overview/CSSOverviewProcessingView.ts
index 4d600e4..3c14bb6 100644
--- a/front_end/panels/css_overview/CSSOverviewProcessingView.ts
+++ b/front_end/panels/css_overview/CSSOverviewProcessingView.ts
@@ -24,7 +24,7 @@
   fragment?: UI.Fragment.Fragment;
   constructor(controller: OverviewController) {
     super();
-    this.registerRequiredCSS('panels/css_overview/cssOverviewProcessingView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/css_overview/cssOverviewProcessingView.css');
 
     this._formatter = new Intl.NumberFormat('en-US');
     this._controller = controller;
diff --git a/front_end/panels/css_overview/CSSOverviewSidebarPanel.ts b/front_end/panels/css_overview/CSSOverviewSidebarPanel.ts
index f193662..adc9dec 100644
--- a/front_end/panels/css_overview/CSSOverviewSidebarPanel.ts
+++ b/front_end/panels/css_overview/CSSOverviewSidebarPanel.ts
@@ -30,7 +30,7 @@
   constructor() {
     super(true);
 
-    this.registerRequiredCSS('panels/css_overview/cssOverviewSidebarPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/css_overview/cssOverviewSidebarPanel.css');
     this.contentElement.classList.add('overview-sidebar-panel');
     this.contentElement.addEventListener('click', this._onItemClick.bind(this));
 
diff --git a/front_end/panels/css_overview/CSSOverviewStartView.ts b/front_end/panels/css_overview/CSSOverviewStartView.ts
index 1e2e70f..783d03d 100644
--- a/front_end/panels/css_overview/CSSOverviewStartView.ts
+++ b/front_end/panels/css_overview/CSSOverviewStartView.ts
@@ -26,7 +26,7 @@
   _controller: OverviewController;
   constructor(controller: OverviewController) {
     super();
-    this.registerRequiredCSS('panels/css_overview/cssOverviewStartView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/css_overview/cssOverviewStartView.css');
 
     this._controller = controller;
     this._render();
diff --git a/front_end/panels/developer_resources/DeveloperResourcesListView.ts b/front_end/panels/developer_resources/DeveloperResourcesListView.ts
index 3c1ca54..915bfff 100644
--- a/front_end/panels/developer_resources/DeveloperResourcesListView.ts
+++ b/front_end/panels/developer_resources/DeveloperResourcesListView.ts
@@ -76,8 +76,7 @@
     this._nodeForItem = new Map();
     this._isVisibleFilter = isVisibleFilter;
     this._highlightRegExp = null;
-    this.registerRequiredCSS(
-        'panels/developer_resources/developerResourcesListView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/developer_resources/developerResourcesListView.css');
 
     const columns = [
       {id: 'status', title: i18nString(UIStrings.status), width: '60px', fixedWidth: true, sortable: true},
diff --git a/front_end/panels/developer_resources/DeveloperResourcesView.ts b/front_end/panels/developer_resources/DeveloperResourcesView.ts
index fa480ab..fbc2564 100644
--- a/front_end/panels/developer_resources/DeveloperResourcesView.ts
+++ b/front_end/panels/developer_resources/DeveloperResourcesView.ts
@@ -56,7 +56,7 @@
   _loader: SDK.PageResourceLoader.PageResourceLoader;
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/developer_resources/developerResourcesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/developer_resources/developerResourcesView.css');
 
     const toolbarContainer = this.contentElement.createChild('div', 'developer-resource-view-toolbar-container');
     const toolbar = new UI.Toolbar.Toolbar('developer-resource-view-toolbar', toolbarContainer);
diff --git a/front_end/panels/elements/ClassesPaneWidget.ts b/front_end/panels/elements/ClassesPaneWidget.ts
index f3a3a78..9bc84f0 100644
--- a/front_end/panels/elements/ClassesPaneWidget.ts
+++ b/front_end/panels/elements/ClassesPaneWidget.ts
@@ -47,7 +47,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/elements/classesPaneWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/classesPaneWidget.css');
     this.contentElement.className = 'styles-element-classes-pane';
     const container = this.contentElement.createChild('div', 'title-container');
     this._input = container.createChild('div', 'new-class-input monospace');
diff --git a/front_end/panels/elements/ComputedStyleWidget.ts b/front_end/panels/elements/ComputedStyleWidget.ts
index d0fa181..898db8a 100644
--- a/front_end/panels/elements/ComputedStyleWidget.ts
+++ b/front_end/panels/elements/ComputedStyleWidget.ts
@@ -190,7 +190,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/elements/computedStyleSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/computedStyleSidebarPane.css');
 
     this._computedStyleModel = new ComputedStyleModel();
     this._computedStyleModel.addEventListener(Events.ComputedStyleChanged, this.update, this);
@@ -226,8 +226,7 @@
     this._propertiesOutline.hideOverflow();
     this._propertiesOutline.setShowSelectionOnKeyboardFocus(true);
     this._propertiesOutline.setFocusable(true);
-    this._propertiesOutline.registerRequiredCSS(
-        'panels/elements/computedStyleWidgetTree.css', {enableLegacyPatching: false});
+    this._propertiesOutline.registerRequiredCSS('panels/elements/computedStyleWidgetTree.css');
     this._propertiesOutline.element.classList.add('monospace', 'computed-properties');
     this._propertiesOutline.addEventListener(UI.TreeOutline.Events.ElementExpanded, this._onTreeElementToggled, this);
     this._propertiesOutline.addEventListener(UI.TreeOutline.Events.ElementCollapsed, this._onTreeElementToggled, this);
diff --git a/front_end/panels/elements/DOMLinkifier.ts b/front_end/panels/elements/DOMLinkifier.ts
index 5ddf825..7d02093 100644
--- a/front_end/panels/elements/DOMLinkifier.ts
+++ b/front_end/panels/elements/DOMLinkifier.ts
@@ -83,7 +83,7 @@
   const root = document.createElement('span');
   root.classList.add('monospace');
   const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-      root, {cssFile: 'panels/elements/domLinkifier.css', enableLegacyPatching: false, delegatesFocus: undefined});
+      root, {cssFile: 'panels/elements/domLinkifier.css', delegatesFocus: undefined});
   const link = (shadowRoot.createChild('div', 'node-link') as HTMLDivElement);
 
   decorateNodeLabel(node, link, options.tooltip);
@@ -111,7 +111,7 @@
     }): Node {
   const root = document.createElement('div');
   const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-      root, {cssFile: 'panels/elements/domLinkifier.css', enableLegacyPatching: false, delegatesFocus: undefined});
+      root, {cssFile: 'panels/elements/domLinkifier.css', delegatesFocus: undefined});
   const link = (shadowRoot.createChild('div', 'node-link') as HTMLDivElement);
   link.createChild('slot');
   link.addEventListener('click', deferredNode.resolve.bind(deferredNode, onDeferredNodeResolved), false);
diff --git a/front_end/panels/elements/ElementStatePaneWidget.ts b/front_end/panels/elements/ElementStatePaneWidget.ts
index 2788fc2..b8369d3 100644
--- a/front_end/panels/elements/ElementStatePaneWidget.ts
+++ b/front_end/panels/elements/ElementStatePaneWidget.ts
@@ -31,7 +31,7 @@
   _cssModel?: SDK.CSSModel.CSSModel|null;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/elements/elementStatePaneWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/elementStatePaneWidget.css');
     this.contentElement.className = 'styles-element-state-pane';
     UI.UIUtils.createTextChild(this.contentElement.createChild('div'), i18nString(UIStrings.forceElementState));
     const table = document.createElement('table');
diff --git a/front_end/panels/elements/ElementsPanel.ts b/front_end/panels/elements/ElementsPanel.ts
index a34a333..7194adf 100644
--- a/front_end/panels/elements/ElementsPanel.ts
+++ b/front_end/panels/elements/ElementsPanel.ts
@@ -180,7 +180,7 @@
 
   constructor() {
     super('elements');
-    this.registerRequiredCSS('panels/elements/elementsPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/elementsPanel.css');
     this._splitWidget = new UI.SplitWidget.SplitWidget(true, true, 'elementsPanelSplitViewState', 325, 325);
     this._splitWidget.addEventListener(
         UI.SplitWidget.Events.SidebarSizeChanged, this._updateTreeOutlineVisibleWidth.bind(this));
diff --git a/front_end/panels/elements/ElementsTreeOutline.ts b/front_end/panels/elements/ElementsTreeOutline.ts
index 11e34d9..4a53221 100644
--- a/front_end/panels/elements/ElementsTreeOutline.ts
+++ b/front_end/panels/elements/ElementsTreeOutline.ts
@@ -103,8 +103,7 @@
     this.treeElementByNode = new WeakMap();
     const shadowContainer = document.createElement('div');
     this._shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        shadowContainer,
-        {cssFile: 'panels/elements/elementsTreeOutline.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        shadowContainer, {cssFile: 'panels/elements/elementsTreeOutline.css', delegatesFocus: undefined});
     const outlineDisclosureElement = this._shadowRoot.createChild('div', 'elements-disclosure');
 
     this._element = this.element;
diff --git a/front_end/panels/elements/MetricsSidebarPane.ts b/front_end/panels/elements/MetricsSidebarPane.ts
index a371ce2..6dc7de8 100644
--- a/front_end/panels/elements/MetricsSidebarPane.ts
+++ b/front_end/panels/elements/MetricsSidebarPane.ts
@@ -53,7 +53,7 @@
 
   constructor() {
     super();
-    this.registerRequiredCSS('panels/elements/metricsSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/metricsSidebarPane.css');
 
     this.originalPropertyData = null;
     this.previousPropertyDataCandidate = null;
diff --git a/front_end/panels/elements/NodeStackTraceWidget.ts b/front_end/panels/elements/NodeStackTraceWidget.ts
index d009098..879c905 100644
--- a/front_end/panels/elements/NodeStackTraceWidget.ts
+++ b/front_end/panels/elements/NodeStackTraceWidget.ts
@@ -26,7 +26,7 @@
 
   constructor() {
     super(true /* isWebComponent */);
-    this.registerRequiredCSS('panels/elements/nodeStackTraceWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/nodeStackTraceWidget.css');
 
     this._noStackTraceElement = this.contentElement.createChild('div', 'gray-info-message');
     this._noStackTraceElement.textContent = i18nString(UIStrings.noStackTraceAvailable);
diff --git a/front_end/panels/elements/PlatformFontsWidget.ts b/front_end/panels/elements/PlatformFontsWidget.ts
index f053916..2ca1257 100644
--- a/front_end/panels/elements/PlatformFontsWidget.ts
+++ b/front_end/panels/elements/PlatformFontsWidget.ts
@@ -66,7 +66,7 @@
 
   constructor(sharedModel: ComputedStyleModel) {
     super(true);
-    this.registerRequiredCSS('panels/elements/platformFontsWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/platformFontsWidget.css');
 
     this._sharedModel = sharedModel;
     this._sharedModel.addEventListener(Events.ComputedStyleChanged, this.update, this);
diff --git a/front_end/panels/elements/PropertiesWidget.ts b/front_end/panels/elements/PropertiesWidget.ts
index 049ac38..aa22f55 100644
--- a/front_end/panels/elements/PropertiesWidget.ts
+++ b/front_end/panels/elements/PropertiesWidget.ts
@@ -48,7 +48,7 @@
   _lastRequestedNode?: SDK.DOMModel.DOMNode;
   constructor() {
     super(true /* isWebComponent */);
-    this.registerRequiredCSS('panels/elements/propertiesWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/propertiesWidget.css');
 
     SDK.TargetManager.TargetManager.instance().addModelListener(
         SDK.DOMModel.DOMModel, SDK.DOMModel.Events.AttrModified, this._onNodeChange, this);
diff --git a/front_end/panels/elements/StylesSidebarPane.ts b/front_end/panels/elements/StylesSidebarPane.ts
index 300291c..7c3e8c5 100644
--- a/front_end/panels/elements/StylesSidebarPane.ts
+++ b/front_end/panels/elements/StylesSidebarPane.ts
@@ -228,7 +228,7 @@
   private constructor() {
     super(true /* delegatesFocus */);
     this.setMinimumSize(96, 26);
-    this.registerRequiredCSS('panels/elements/stylesSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/elements/stylesSidebarPane.css');
 
     Common.Settings.Settings.instance().moduleSetting('colorFormat').addChangeListener(this.update.bind(this));
     Common.Settings.Settings.instance().moduleSetting('textEditorIndent').addChangeListener(this.update.bind(this));
@@ -1212,8 +1212,7 @@
 
     this.propertiesTreeOutline = new UI.TreeOutline.TreeOutlineInShadow();
     this.propertiesTreeOutline.setFocusable(false);
-    this.propertiesTreeOutline.registerRequiredCSS(
-        'panels/elements/stylesSectionTree.css', {enableLegacyPatching: false});
+    this.propertiesTreeOutline.registerRequiredCSS('panels/elements/stylesSectionTree.css');
     this.propertiesTreeOutline.element.classList.add('style-properties', 'matched-styles', 'monospace');
     // @ts-ignore TODO: fix ad hoc section property in a separate CL to be safe
     this.propertiesTreeOutline.section = this;
diff --git a/front_end/panels/elements/components/LayoutPane.ts b/front_end/panels/elements/components/LayoutPane.ts
index bb1f020..8a1f11c 100644
--- a/front_end/panels/elements/components/LayoutPane.ts
+++ b/front_end/panels/elements/components/LayoutPane.ts
@@ -90,9 +90,9 @@
   constructor() {
     super();
     this.shadow.adoptedStyleSheets = [
-      ...getStyleSheets('panels/elements/layoutPane.css', {enableLegacyPatching: false}),
+      ...getStyleSheets('panels/elements/layoutPane.css'),
       // Required for chrome-select styles.
-      ...getStyleSheets('ui/legacy/inspectorCommon.css', {enableLegacyPatching: false}),
+      ...getStyleSheets('ui/legacy/inspectorCommon.css'),
     ];
   }
 
diff --git a/front_end/panels/emulation/DeviceModeToolbar.ts b/front_end/panels/emulation/DeviceModeToolbar.ts
index a3fb1d9..4fdf1b3 100644
--- a/front_end/panels/emulation/DeviceModeToolbar.ts
+++ b/front_end/panels/emulation/DeviceModeToolbar.ts
@@ -540,8 +540,7 @@
   _wrapToolbarItem(element: Element): UI.Toolbar.ToolbarItem {
     const container = document.createElement('div');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        container,
-        {cssFile: 'panels/emulation/deviceModeToolbar.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        container, {cssFile: 'panels/emulation/deviceModeToolbar.css', delegatesFocus: undefined});
     shadowRoot.appendChild(element);
     return new UI.Toolbar.ToolbarItem(container);
   }
diff --git a/front_end/panels/emulation/DeviceModeView.ts b/front_end/panels/emulation/DeviceModeView.ts
index 63aaf56..a08f677 100644
--- a/front_end/panels/emulation/DeviceModeView.ts
+++ b/front_end/panels/emulation/DeviceModeView.ts
@@ -100,7 +100,7 @@
 
     this.setMinimumSize(150, 150);
     this.element.classList.add('device-mode-view');
-    this.registerRequiredCSS('panels/emulation/deviceModeView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/emulation/deviceModeView.css');
     UI.Tooltip.Tooltip.addNativeOverrideContainer(this.contentElement);
 
     this._model = DeviceModeModel.instance();
diff --git a/front_end/panels/emulation/DevicesSettingsTab.ts b/front_end/panels/emulation/DevicesSettingsTab.ts
index 26b600a..f5e8a03 100644
--- a/front_end/panels/emulation/DevicesSettingsTab.ts
+++ b/front_end/panels/emulation/DevicesSettingsTab.ts
@@ -76,7 +76,7 @@
     super();
     this.element.classList.add('settings-tab-container');
     this.element.classList.add('devices-settings-tab');
-    this.registerRequiredCSS('panels/emulation/devicesSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/emulation/devicesSettingsTab.css');
 
     const header = this.element.createChild('header');
     UI.UIUtils.createTextChild(header.createChild('h1'), i18nString(UIStrings.emulatedDevices));
@@ -90,7 +90,7 @@
     buttonsRow.appendChild(this._addCustomButton);
 
     this._list = new UI.ListWidget.ListWidget(this, false /* delegatesFocus */);
-    this._list.registerRequiredCSS('panels/emulation/devicesSettingsTab.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('panels/emulation/devicesSettingsTab.css');
     this._list.element.classList.add('devices-list');
     this._list.show(this.containerElement);
 
diff --git a/front_end/panels/emulation/InspectedPagePlaceholder.ts b/front_end/panels/emulation/InspectedPagePlaceholder.ts
index c0b6187..e003936 100644
--- a/front_end/panels/emulation/InspectedPagePlaceholder.ts
+++ b/front_end/panels/emulation/InspectedPagePlaceholder.ts
@@ -12,7 +12,7 @@
   _updateId?: number;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/emulation/inspectedPagePlaceholder.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/emulation/inspectedPagePlaceholder.css');
     UI.ZoomManager.ZoomManager.instance().addEventListener(UI.ZoomManager.Events.ZoomChanged, this.onResize, this);
     this.restoreMinimumSize();
   }
diff --git a/front_end/panels/emulation/LocationsSettingsTab.ts b/front_end/panels/emulation/LocationsSettingsTab.ts
index 9b5e210..10b5276 100644
--- a/front_end/panels/emulation/LocationsSettingsTab.ts
+++ b/front_end/panels/emulation/LocationsSettingsTab.ts
@@ -108,7 +108,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/emulation/locationsSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/emulation/locationsSettingsTab.css');
 
     this.contentElement.createChild('div', 'header').textContent = i18nString(UIStrings.customLocations);
 
@@ -118,7 +118,7 @@
 
     this._list = new UI.ListWidget.ListWidget(this);
     this._list.element.classList.add('locations-list');
-    this._list.registerRequiredCSS('panels/emulation/locationsSettingsTab.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('panels/emulation/locationsSettingsTab.css');
     this._list.show(this.contentElement);
     this._customSetting =
         (Common.Settings.Settings.instance().moduleSetting('emulation.locations') as
diff --git a/front_end/panels/emulation/MediaQueryInspector.ts b/front_end/panels/emulation/MediaQueryInspector.ts
index b11e3cb..01449dd 100644
--- a/front_end/panels/emulation/MediaQueryInspector.ts
+++ b/front_end/panels/emulation/MediaQueryInspector.ts
@@ -34,7 +34,7 @@
 
   constructor(getWidthCallback: () => number, setWidthCallback: (arg0: number) => void) {
     super(true);
-    this.registerRequiredCSS('panels/emulation/mediaQueryInspector.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/emulation/mediaQueryInspector.css');
     this.contentElement.classList.add('media-inspector-view');
     this.contentElement.addEventListener('click', this._onMediaQueryClicked.bind(this), false);
     this.contentElement.addEventListener('contextmenu', this._onContextMenu.bind(this), false);
diff --git a/front_end/panels/emulation/SensorsView.ts b/front_end/panels/emulation/SensorsView.ts
index 2c3001a..64d882e 100644
--- a/front_end/panels/emulation/SensorsView.ts
+++ b/front_end/panels/emulation/SensorsView.ts
@@ -208,7 +208,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/emulation/sensors.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/emulation/sensors.css');
     this.contentElement.classList.add('sensors-view');
 
     this._LocationSetting = Common.Settings.Settings.instance().createSetting('emulation.locationOverride', '');
diff --git a/front_end/panels/event_listeners/EventListenersView.ts b/front_end/panels/event_listeners/EventListenersView.ts
index 7252db9..a93d09f 100644
--- a/front_end/panels/event_listeners/EventListenersView.ts
+++ b/front_end/panels/event_listeners/EventListenersView.ts
@@ -60,10 +60,8 @@
     this._enableDefaultTreeFocus = enableDefaultTreeFocus;
     this._treeOutline = new UI.TreeOutline.TreeOutlineInShadow();
     this._treeOutline.hideOverflow();
-    this._treeOutline.registerRequiredCSS(
-        'ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
-    this._treeOutline.registerRequiredCSS(
-        'panels/event_listeners/eventListenersView.css', {enableLegacyPatching: false});
+    this._treeOutline.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
+    this._treeOutline.registerRequiredCSS('panels/event_listeners/eventListenersView.css');
     this._treeOutline.setComparator(EventListenersTreeElement.comparator);
     this._treeOutline.element.classList.add('monospace');
     this._treeOutline.setShowSelectionOnKeyboardFocus(true);
diff --git a/front_end/panels/help/ReleaseNoteView.ts b/front_end/panels/help/ReleaseNoteView.ts
index 5f8d2f6..c20778c 100644
--- a/front_end/panels/help/ReleaseNoteView.ts
+++ b/front_end/panels/help/ReleaseNoteView.ts
@@ -29,7 +29,7 @@
   _releaseNoteElement: Element;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/help/releaseNote.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/help/releaseNote.css');
     this._releaseNoteElement = this._createReleaseNoteElement(latestReleaseNote());
     const topSection = this.contentElement.createChild('div', 'release-note-top-section');
     topSection.textContent = latestReleaseNote().header;
diff --git a/front_end/panels/input/InputTimeline.ts b/front_end/panels/input/InputTimeline.ts
index 274e20f..b819936 100644
--- a/front_end/panels/input/InputTimeline.ts
+++ b/front_end/panels/input/InputTimeline.ts
@@ -49,7 +49,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/input//inputTimeline.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/input//inputTimeline.css');
     this.element.classList.add('inputs-timeline');
 
     this._tracingClient = null;
diff --git a/front_end/panels/issues/CSPViolationsListView.ts b/front_end/panels/issues/CSPViolationsListView.ts
index 98d0db7..0d51f11 100644
--- a/front_end/panels/issues/CSPViolationsListView.ts
+++ b/front_end/panels/issues/CSPViolationsListView.ts
@@ -16,7 +16,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/issues/cspViolationsListView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/issues/cspViolationsListView.css');
 
     this.table.data = {
       columns: [
diff --git a/front_end/panels/issues/CSPViolationsView.ts b/front_end/panels/issues/CSPViolationsView.ts
index 45cabec..dbc76be 100644
--- a/front_end/panels/issues/CSPViolationsView.ts
+++ b/front_end/panels/issues/CSPViolationsView.ts
@@ -28,7 +28,7 @@
    */
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/issues/cspViolationsView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/issues/cspViolationsView.css');
     this.contentElement.classList.add('csp-violations-pane');
 
     const topToolbar = new UI.Toolbar.Toolbar('csp-violations-toolbar', this.contentElement);
diff --git a/front_end/panels/issues/IssuesPane.ts b/front_end/panels/issues/IssuesPane.ts
index e6b77af..9ed32ff 100644
--- a/front_end/panels/issues/IssuesPane.ts
+++ b/front_end/panels/issues/IssuesPane.ts
@@ -166,7 +166,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/issues/issuesPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/issues/issuesPane.css');
     this.contentElement.classList.add('issues-pane');
 
     this.categoryViews = new Map();
@@ -176,7 +176,7 @@
     this.createToolbars();
 
     this.issuesTree = new UI.TreeOutline.TreeOutlineInShadow();
-    this.issuesTree.registerRequiredCSS('panels/issues/issuesTree.css', {enableLegacyPatching: false});
+    this.issuesTree.registerRequiredCSS('panels/issues/issuesTree.css');
     this.issuesTree.setShowSelectionOnKeyboardFocus(true);
     this.issuesTree.contentElement.classList.add('issues');
     this.contentElement.appendChild(this.issuesTree.element);
diff --git a/front_end/panels/layer_viewer/LayerDetailsView.ts b/front_end/panels/layer_viewer/LayerDetailsView.ts
index f1dd79a..b38e7b7 100644
--- a/front_end/panels/layer_viewer/LayerDetailsView.ts
+++ b/front_end/panels/layer_viewer/LayerDetailsView.ts
@@ -171,7 +171,7 @@
 
   constructor(layerViewHost: LayerViewHost) {
     super(true);
-    this.registerRequiredCSS('panels/layer_viewer/layerDetailsView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/layer_viewer/layerDetailsView.css');
     this._layerViewHost = layerViewHost;
     this._layerViewHost.registerView(this);
     this._emptyWidget = new UI.EmptyWidget.EmptyWidget(i18nString(UIStrings.selectALayerToSeeItsDetails));
diff --git a/front_end/panels/layer_viewer/Layers3DView.ts b/front_end/panels/layer_viewer/Layers3DView.ts
index e55b6ea..bef267d 100644
--- a/front_end/panels/layer_viewer/Layers3DView.ts
+++ b/front_end/panels/layer_viewer/Layers3DView.ts
@@ -130,7 +130,7 @@
   constructor(layerViewHost: LayerViewHost) {
     super(true);
 
-    this.registerRequiredCSS('panels/layer_viewer/layers3DView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/layer_viewer/layers3DView.css');
     this.contentElement.classList.add('layers-3d-view');
     this._failBanner = new UI.Widget.VBox();
     this._failBanner.element.classList.add('full-widget-dimmed-banner');
diff --git a/front_end/panels/layer_viewer/PaintProfilerView.ts b/front_end/panels/layer_viewer/PaintProfilerView.ts
index 6937d6f..e6832d5 100644
--- a/front_end/panels/layer_viewer/PaintProfilerView.ts
+++ b/front_end/panels/layer_viewer/PaintProfilerView.ts
@@ -97,7 +97,7 @@
 
   constructor(showImageCallback: (arg0?: string|undefined) => void) {
     super(true);
-    this.registerRequiredCSS('panels/layer_viewer/paintProfiler.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/layer_viewer/paintProfiler.css');
     this.contentElement.classList.add('paint-profiler-overview');
     this._canvasContainer = this.contentElement.createChild('div', 'paint-profiler-canvas-container');
     this._progressBanner = this.contentElement.createChild('div', 'full-widget-dimmed-banner hidden');
diff --git a/front_end/panels/lighthouse/LighthousePanel.ts b/front_end/panels/lighthouse/LighthousePanel.ts
index c7283cd..0170656 100644
--- a/front_end/panels/lighthouse/LighthousePanel.ts
+++ b/front_end/panels/lighthouse/LighthousePanel.ts
@@ -80,8 +80,8 @@
 
   private constructor() {
     super('lighthouse');
-    this.registerRequiredCSS('third_party/lighthouse/report-assets/report.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('panels/lighthouse/lighthousePanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('third_party/lighthouse/report-assets/report.css');
+    this.registerRequiredCSS('panels/lighthouse/lighthousePanel.css');
 
     this._protocolService = new ProtocolService();
     this._controller = new LighthouseController(this._protocolService);
diff --git a/front_end/panels/lighthouse/LighthouseStartView.ts b/front_end/panels/lighthouse/LighthouseStartView.ts
index 31de9be..6dfa1cf 100644
--- a/front_end/panels/lighthouse/LighthouseStartView.ts
+++ b/front_end/panels/lighthouse/LighthouseStartView.ts
@@ -51,7 +51,7 @@
 
   constructor(controller: LighthouseController) {
     super();
-    this.registerRequiredCSS('panels/lighthouse/lighthouseStartView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/lighthouse/lighthouseStartView.css');
     this._controller = controller;
     this._settingsToolbar = new UI.Toolbar.Toolbar('');
     this._render();
diff --git a/front_end/panels/lighthouse/LighthouseStatusView.ts b/front_end/panels/lighthouse/LighthouseStatusView.ts
index d5f1d8f..9564040 100644
--- a/front_end/panels/lighthouse/LighthouseStatusView.ts
+++ b/front_end/panels/lighthouse/LighthouseStatusView.ts
@@ -191,8 +191,7 @@
 
   _render(): void {
     const dialogRoot = UI.Utils.createShadowRootWithCoreStyles(
-        this._dialog.contentElement,
-        {cssFile: 'panels/lighthouse/lighthouseDialog.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        this._dialog.contentElement, {cssFile: 'panels/lighthouse/lighthouseDialog.css', delegatesFocus: undefined});
     const lighthouseViewElement = dialogRoot.createChild('div', 'lighthouse-view vbox');
 
     const cancelButton = UI.UIUtils.createTextButton(i18nString(UIStrings.cancel), this._cancel.bind(this));
diff --git a/front_end/panels/media/EventDisplayTable.ts b/front_end/panels/media/EventDisplayTable.ts
index 57d2ed1..355bbd5 100644
--- a/front_end/panels/media/EventDisplayTable.ts
+++ b/front_end/panels/media/EventDisplayTable.ts
@@ -78,7 +78,7 @@
     super();
 
     // Set up element styles.
-    this.registerRequiredCSS('panels/media/eventDisplayTable.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/media/eventDisplayTable.css');
     this.contentElement.classList.add('event-display-table-contents-table-container');
 
     this._dataGrid = this._createDataGrid([
diff --git a/front_end/panels/media/PlayerListView.ts b/front_end/panels/media/PlayerListView.ts
index 792f511..d74c3a1 100644
--- a/front_end/panels/media/PlayerListView.ts
+++ b/front_end/panels/media/PlayerListView.ts
@@ -103,7 +103,7 @@
     // The parent tree for storing sections
     this._sidebarTree = new UI.TreeOutline.TreeOutlineInShadow();
     this.contentElement.appendChild(this._sidebarTree.element);
-    this._sidebarTree.registerRequiredCSS('panels/media/playerListView.css', {enableLegacyPatching: false});
+    this._sidebarTree.registerRequiredCSS('panels/media/playerListView.css');
 
     // Players active in this tab.
     this._playerList = this._addListSection(i18nString(UIStrings.players));
diff --git a/front_end/panels/media/PlayerMessagesView.ts b/front_end/panels/media/PlayerMessagesView.ts
index 2d16af0..a73483c 100644
--- a/front_end/panels/media/PlayerMessagesView.ts
+++ b/front_end/panels/media/PlayerMessagesView.ts
@@ -203,8 +203,7 @@
   createElementForItem(item: SelectableLevel): Element {
     const element = document.createElement('div');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        element,
-        {cssFile: 'panels/media/playerMessagesView.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        element, {cssFile: 'panels/media/playerMessagesView.css', delegatesFocus: undefined});
     const container = shadowRoot.createChild('div', 'media-messages-level-dropdown-element');
     const checkBox = container.createChild('div', 'media-messages-level-dropdown-checkbox') as HTMLElement;
     const text = container.createChild('span', 'media-messages-level-dropdown-text');
@@ -238,7 +237,7 @@
 
   constructor() {
     super();
-    this.registerRequiredCSS('panels/media/playerMessagesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/media/playerMessagesView.css');
 
     this._headerPanel = this.contentElement.createChild('div', 'media-messages-header');
     this._bodyPanel = this.contentElement.createChild('div', 'media-messages-body');
diff --git a/front_end/panels/media/PlayerPropertiesView.ts b/front_end/panels/media/PlayerPropertiesView.ts
index 58f1746..447c6d9 100644
--- a/front_end/panels/media/PlayerPropertiesView.ts
+++ b/front_end/panels/media/PlayerPropertiesView.ts
@@ -439,7 +439,7 @@
   constructor() {
     super();
     this.contentElement.classList.add('media-properties-frame');
-    this.registerRequiredCSS('panels/media/playerPropertiesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/media/playerPropertiesView.css');
     this._mediaElements = [];
     this._videoDecoderElements = [];
     this._audioDecoderElements = [];
diff --git a/front_end/panels/mobile_throttling/ThrottlingSettingsTab.ts b/front_end/panels/mobile_throttling/ThrottlingSettingsTab.ts
index c457789..33d5de0 100644
--- a/front_end/panels/mobile_throttling/ThrottlingSettingsTab.ts
+++ b/front_end/panels/mobile_throttling/ThrottlingSettingsTab.ts
@@ -88,7 +88,7 @@
   _editor?: UI.ListWidget.Editor<SDK.NetworkManager.Conditions>;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/mobile_throttling/throttlingSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/mobile_throttling/throttlingSettingsTab.css');
 
     const header = this.contentElement.createChild('div', 'header');
     header.textContent = i18nString(UIStrings.networkThrottlingProfiles);
@@ -100,7 +100,7 @@
 
     this._list = new UI.ListWidget.ListWidget(this);
     this._list.element.classList.add('conditions-list');
-    this._list.registerRequiredCSS('panels/mobile_throttling/throttlingSettingsTab.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('panels/mobile_throttling/throttlingSettingsTab.css');
     this._list.show(this.contentElement);
 
     this._customSetting = Common.Settings.Settings.instance().moduleSetting('customNetworkConditions');
diff --git a/front_end/panels/network/BinaryResourceView.ts b/front_end/panels/network/BinaryResourceView.ts
index 144beca..c539a1f 100644
--- a/front_end/panels/network/BinaryResourceView.ts
+++ b/front_end/panels/network/BinaryResourceView.ts
@@ -71,7 +71,7 @@
 
   constructor(base64content: string, contentUrl: string, resourceType: Common.ResourceType.ResourceType) {
     super();
-    this.registerRequiredCSS('panels/network/binaryResourceView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/binaryResourceView.css');
 
     this._binaryResourceViewFactory =
         new SourceFrame.BinaryResourceViewFactory.BinaryResourceViewFactory(base64content, contentUrl, resourceType);
diff --git a/front_end/panels/network/BlockedURLsPane.ts b/front_end/panels/network/BlockedURLsPane.ts
index c731503..d456aa7 100644
--- a/front_end/panels/network/BlockedURLsPane.ts
+++ b/front_end/panels/network/BlockedURLsPane.ts
@@ -69,7 +69,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/network/blockedURLsPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/blockedURLsPane.css');
 
     this._manager = SDK.NetworkManager.MultitargetNetworkManager.instance();
     this._manager.addEventListener(SDK.NetworkManager.MultitargetNetworkManager.Events.BlockedPatternsChanged, () => {
@@ -90,7 +90,7 @@
 
     this._list = new UI.ListWidget.ListWidget(this);
     this._list.element.classList.add('blocked-urls');
-    this._list.registerRequiredCSS('panels/network/blockedURLsPane.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('panels/network/blockedURLsPane.css');
     this._list.setEmptyPlaceholder(this._createEmptyPlaceholder());
     this._list.show(this.contentElement);
 
diff --git a/front_end/panels/network/EventSourceMessagesView.ts b/front_end/panels/network/EventSourceMessagesView.ts
index ea0ba7e..a9ee514 100644
--- a/front_end/panels/network/EventSourceMessagesView.ts
+++ b/front_end/panels/network/EventSourceMessagesView.ts
@@ -45,7 +45,7 @@
 
   constructor(request: SDK.NetworkRequest.NetworkRequest) {
     super();
-    this.registerRequiredCSS('panels/network/eventSourceMessagesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/eventSourceMessagesView.css');
     this.element.classList.add('event-source-messages-view');
     this._request = request;
 
diff --git a/front_end/panels/network/NetworkConfigView.ts b/front_end/panels/network/NetworkConfigView.ts
index 4339970..ddf3183 100644
--- a/front_end/panels/network/NetworkConfigView.ts
+++ b/front_end/panels/network/NetworkConfigView.ts
@@ -59,7 +59,7 @@
 export class NetworkConfigView extends UI.Widget.VBox {
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/network/networkConfigView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/networkConfigView.css');
     this.contentElement.classList.add('network-config');
 
     this._createCacheSection();
diff --git a/front_end/panels/network/NetworkLogView.ts b/front_end/panels/network/NetworkLogView.ts
index e4a2748..8a88f59 100644
--- a/front_end/panels/network/NetworkLogView.ts
+++ b/front_end/panels/network/NetworkLogView.ts
@@ -380,7 +380,7 @@
       networkLogLargeRowsSetting: Common.Settings.Setting<boolean>) {
     super();
     this.setMinimumSize(50, 64);
-    this.registerRequiredCSS('panels/network/networkLogView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/networkLogView.css');
 
     this.element.id = 'network-container';
     this.element.classList.add('no-node-selected');
diff --git a/front_end/panels/network/NetworkManageCustomHeadersView.ts b/front_end/panels/network/NetworkManageCustomHeadersView.ts
index 41eb0f2..eb2ebb7 100644
--- a/front_end/panels/network/NetworkManageCustomHeadersView.ts
+++ b/front_end/panels/network/NetworkManageCustomHeadersView.ts
@@ -52,14 +52,14 @@
       changeHeaderColumnCallback: (arg0: string, arg1: string) => boolean,
       removeHeaderColumnCallback: (arg0: string) => boolean) {
     super(true);
-    this.registerRequiredCSS('panels/network/networkManageCustomHeadersView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/networkManageCustomHeadersView.css');
 
     this.contentElement.classList.add('custom-headers-wrapper');
     this.contentElement.createChild('div', 'header').textContent = i18nString(UIStrings.manageHeaderColumns);
 
     this._list = new UI.ListWidget.ListWidget(this);
     this._list.element.classList.add('custom-headers-list');
-    this._list.registerRequiredCSS('panels/network/networkManageCustomHeadersView.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('panels/network/networkManageCustomHeadersView.css');
 
     const placeholder = document.createElement('div');
     placeholder.classList.add('custom-headers-list-list-empty');
diff --git a/front_end/panels/network/NetworkPanel.ts b/front_end/panels/network/NetworkPanel.ts
index 6618afe..18d767d 100644
--- a/front_end/panels/network/NetworkPanel.ts
+++ b/front_end/panels/network/NetworkPanel.ts
@@ -197,7 +197,7 @@
 
   constructor() {
     super('network');
-    this.registerRequiredCSS('panels/network/networkPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/networkPanel.css');
 
     this._networkLogShowOverviewSetting =
         Common.Settings.Settings.instance().createSetting('networkLogShowOverview', true);
diff --git a/front_end/panels/network/NetworkWaterfallColumn.ts b/front_end/panels/network/NetworkWaterfallColumn.ts
index 7b6217d..5118ed9 100644
--- a/front_end/panels/network/NetworkWaterfallColumn.ts
+++ b/front_end/panels/network/NetworkWaterfallColumn.ts
@@ -49,7 +49,7 @@
   constructor(calculator: NetworkTimeCalculator) {
     // TODO(allada) Make this a shadowDOM when the NetworkWaterfallColumn gets moved into NetworkLogViewColumns.
     super(false);
-    this.registerRequiredCSS('panels/network/networkWaterfallColumn.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/networkWaterfallColumn.css');
     this._canvas = (this.contentElement.createChild('canvas') as HTMLCanvasElement);
     this._canvas.tabIndex = -1;
     this.setDefaultFocusedElement(this._canvas);
diff --git a/front_end/panels/network/RequestCookiesView.ts b/front_end/panels/network/RequestCookiesView.ts
index 598acab..54d8f7f 100644
--- a/front_end/panels/network/RequestCookiesView.ts
+++ b/front_end/panels/network/RequestCookiesView.ts
@@ -96,7 +96,7 @@
 
   constructor(request: SDK.NetworkRequest.NetworkRequest) {
     super();
-    this.registerRequiredCSS('panels/network/requestCookiesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/requestCookiesView.css');
     this.element.classList.add('request-cookies-view');
 
     this._request = request;
diff --git a/front_end/panels/network/RequestHTMLView.ts b/front_end/panels/network/RequestHTMLView.ts
index e46f7b4..2243801 100644
--- a/front_end/panels/network/RequestHTMLView.ts
+++ b/front_end/panels/network/RequestHTMLView.ts
@@ -36,7 +36,7 @@
   _dataURL: string;
   constructor(dataURL: string) {
     super(true);
-    this.registerRequiredCSS('panels/network/requestHTMLView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/requestHTMLView.css');
     this._dataURL = encodeURI(dataURL).replace(/#/g, '%23');
     this.contentElement.classList.add('html', 'request-view');
   }
diff --git a/front_end/panels/network/RequestHeadersView.ts b/front_end/panels/network/RequestHeadersView.ts
index 9efe20d..8a1bfb1 100644
--- a/front_end/panels/network/RequestHeadersView.ts
+++ b/front_end/panels/network/RequestHeadersView.ts
@@ -256,7 +256,7 @@
 
   constructor(request: SDK.NetworkRequest.NetworkRequest) {
     super();
-    this.registerRequiredCSS('panels/network/requestHeadersView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/requestHeadersView.css');
     this.element.classList.add('request-headers-view');
 
     this._request = request;
@@ -272,10 +272,9 @@
     this._highlightedElement = null;
 
     const root = new UI.TreeOutline.TreeOutlineInShadow();
-    root.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
-    root.registerRequiredCSS(
-        'ui/legacy/components/object_ui/objectPropertiesSection.css', {enableLegacyPatching: false});
-    root.registerRequiredCSS('panels/network/requestHeadersTree.css', {enableLegacyPatching: false});
+    root.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
+    root.registerRequiredCSS('ui/legacy/components/object_ui/objectPropertiesSection.css');
+    root.registerRequiredCSS('panels/network/requestHeadersTree.css');
     root.element.classList.add('request-headers-tree');
     root.makeDense();
     this.element.appendChild(root.element);
diff --git a/front_end/panels/network/RequestInitiatorView.ts b/front_end/panels/network/RequestInitiatorView.ts
index aeffef1..4da5695 100644
--- a/front_end/panels/network/RequestInitiatorView.ts
+++ b/front_end/panels/network/RequestInitiatorView.ts
@@ -34,7 +34,7 @@
 
   constructor(request: SDK.NetworkRequest.NetworkRequest) {
     super();
-    this.registerRequiredCSS('panels/network/requestInitiatorView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/requestInitiatorView.css');
     this.element.classList.add('request-initiator-view');
     this._linkifier = new Components.Linkifier.Linkifier();
     this._request = request;
@@ -61,7 +61,7 @@
 
   _createTree(): UI.TreeOutline.TreeOutlineInShadow {
     const treeOutline = new UI.TreeOutline.TreeOutlineInShadow();
-    treeOutline.registerRequiredCSS('panels/network/requestInitiatorViewTree.css', {enableLegacyPatching: false});
+    treeOutline.registerRequiredCSS('panels/network/requestInitiatorViewTree.css');
     treeOutline.contentElement.classList.add('request-initiator-view-tree');
 
     return treeOutline;
diff --git a/front_end/panels/network/RequestTimingView.ts b/front_end/panels/network/RequestTimingView.ts
index 6e77513..1b26d7f 100644
--- a/front_end/panels/network/RequestTimingView.ts
+++ b/front_end/panels/network/RequestTimingView.ts
@@ -356,7 +356,7 @@
   static createTimingTable(request: SDK.NetworkRequest.NetworkRequest, calculator: NetworkTimeCalculator): Element {
     const tableElement = document.createElement('table');
     tableElement.classList.add('network-timing-table');
-    UI.Utils.appendStyle(tableElement, 'panels/network/networkTimingTable.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(tableElement, 'panels/network/networkTimingTable.css');
     const colgroup = tableElement.createChild('colgroup');
     colgroup.createChild('col', 'labels');
     colgroup.createChild('col', 'bars');
diff --git a/front_end/panels/network/ResourceWebSocketFrameView.ts b/front_end/panels/network/ResourceWebSocketFrameView.ts
index d0e00dd..a91462f 100644
--- a/front_end/panels/network/ResourceWebSocketFrameView.ts
+++ b/front_end/panels/network/ResourceWebSocketFrameView.ts
@@ -162,7 +162,7 @@
 
   constructor(request: SDK.NetworkRequest.NetworkRequest) {
     super();
-    this.registerRequiredCSS('panels/network/webSocketFrameView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/webSocketFrameView.css');
     this.element.classList.add('websocket-frame-view');
     this._request = request;
 
diff --git a/front_end/panels/network/SignedExchangeInfoView.ts b/front_end/panels/network/SignedExchangeInfoView.ts
index ea76e9a..f29a418 100644
--- a/front_end/panels/network/SignedExchangeInfoView.ts
+++ b/front_end/panels/network/SignedExchangeInfoView.ts
@@ -107,11 +107,11 @@
     console.assert(request.signedExchangeInfo() !== null);
     const signedExchangeInfo = (request.signedExchangeInfo() as Protocol.Network.SignedExchangeInfo);
 
-    this.registerRequiredCSS('panels/network/signedExchangeInfoView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/network/signedExchangeInfoView.css');
     this.element.classList.add('signed-exchange-info-view');
 
     const root = new UI.TreeOutline.TreeOutlineInShadow();
-    root.registerRequiredCSS('panels/network/signedExchangeInfoTree.css', {enableLegacyPatching: false});
+    root.registerRequiredCSS('panels/network/signedExchangeInfoTree.css');
     root.element.classList.add('signed-exchange-info-tree');
     root.setFocusable(false);
     root.makeDense();
diff --git a/front_end/panels/performance_monitor/PerformanceMonitor.ts b/front_end/panels/performance_monitor/PerformanceMonitor.ts
index 083ad8c..d009aa8 100644
--- a/front_end/panels/performance_monitor/PerformanceMonitor.ts
+++ b/front_end/panels/performance_monitor/PerformanceMonitor.ts
@@ -79,7 +79,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/performance_monitor/performanceMonitor.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/performance_monitor/performanceMonitor.css');
     this.contentElement.classList.add('perfmon-pane');
     this._metricsBuffer = [];
     /** @const */
diff --git a/front_end/panels/profiler/LiveHeapProfileView.ts b/front_end/panels/profiler/LiveHeapProfileView.ts
index 2a49ca9..fa8f63a 100644
--- a/front_end/panels/profiler/LiveHeapProfileView.ts
+++ b/front_end/panels/profiler/LiveHeapProfileView.ts
@@ -67,7 +67,7 @@
   private constructor() {
     super(true);
     this._gridNodeByUrl = new Map();
-    this.registerRequiredCSS('panels/profiler/liveHeapProfile.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/profiler/liveHeapProfile.css');
 
     this._setting = Common.Settings.Settings.instance().moduleSetting('memoryLiveHeapProfile');
     const toolbar = new UI.Toolbar.Toolbar('live-heap-profile-toolbar', this.contentElement);
diff --git a/front_end/panels/profiler/ProfileLauncherView.ts b/front_end/panels/profiler/ProfileLauncherView.ts
index 0aa04af..3c20a3c 100644
--- a/front_end/panels/profiler/ProfileLauncherView.ts
+++ b/front_end/panels/profiler/ProfileLauncherView.ts
@@ -85,7 +85,7 @@
 
   constructor(profilesPanel: ProfilesPanel) {
     super();
-    this.registerRequiredCSS('panels/profiler/profileLauncherView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/profiler/profileLauncherView.css');
 
     this._panel = profilesPanel;
     this.element.classList.add('profile-launcher-view');
diff --git a/front_end/panels/profiler/ProfilesPanel.ts b/front_end/panels/profiler/ProfilesPanel.ts
index e6c15e4..addde88 100644
--- a/front_end/panels/profiler/ProfilesPanel.ts
+++ b/front_end/panels/profiler/ProfilesPanel.ts
@@ -100,9 +100,9 @@
   constructor(name: string, profileTypes: ProfileType[], recordingActionId: string) {
     super(name);
     this._profileTypes = profileTypes;
-    this.registerRequiredCSS('panels/profiler/heapProfiler.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('panels/profiler/profilesPanel.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/profiler/heapProfiler.css');
+    this.registerRequiredCSS('panels/profiler/profilesPanel.css');
+    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
 
     const mainContainer = new UI.Widget.VBox();
     this.splitWidget().setMainWidget(mainContainer);
@@ -110,7 +110,7 @@
     this.profilesItemTreeElement = new ProfilesSidebarTreeElement(this);
 
     this._sidebarTree = new UI.TreeOutline.TreeOutlineInShadow();
-    this._sidebarTree.registerRequiredCSS('panels/profiler/profilesSidebarTree.css', {enableLegacyPatching: false});
+    this._sidebarTree.registerRequiredCSS('panels/profiler/profilesSidebarTree.css');
     this._sidebarTree.element.classList.add('profiles-sidebar-tree-box');
     this.panelSidebarElement().appendChild(this._sidebarTree.element);
 
diff --git a/front_end/panels/protocol_monitor/ProtocolMonitor.ts b/front_end/panels/protocol_monitor/ProtocolMonitor.ts
index 1af2a3b..32a3b0b 100644
--- a/front_end/panels/protocol_monitor/ProtocolMonitor.ts
+++ b/front_end/panels/protocol_monitor/ProtocolMonitor.ts
@@ -125,7 +125,7 @@
     this._startTime = 0;
     this._dataGridRowForId = new Map();
     const topToolbar = new UI.Toolbar.Toolbar('protocol-monitor-toolbar', this.contentElement);
-    this.registerRequiredCSS('panels/protocol_monitor/protocolMonitor.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/protocol_monitor/protocolMonitor.css');
     this.contentElement.classList.add('protocol-monitor');
     const recordButton = new UI.Toolbar.ToolbarToggle(
         i18nString(UIStrings.record), 'largeicon-start-recording', 'largeicon-stop-recording');
diff --git a/front_end/panels/recorder/RecorderPanel.ts b/front_end/panels/recorder/RecorderPanel.ts
index 71620bb..018d70e 100644
--- a/front_end/panels/recorder/RecorderPanel.ts
+++ b/front_end/panels/recorder/RecorderPanel.ts
@@ -23,7 +23,7 @@
 
   constructor() {
     super('recorder');
-    this.registerRequiredCSS('panels/recorder/recorderPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/recorder/recorderPanel.css');
 
     const mainContainer = new UI.Widget.VBox();
     mainContainer.show(this.element);
diff --git a/front_end/panels/screencast/ScreencastView.ts b/front_end/panels/screencast/ScreencastView.ts
index a70c457..8951001 100644
--- a/front_end/panels/screencast/ScreencastView.ts
+++ b/front_end/panels/screencast/ScreencastView.ts
@@ -130,7 +130,7 @@
     this._inputModel = screenCaptureModel.target().model(InputModel);
 
     this.setMinimumSize(150, 150);
-    this.registerRequiredCSS('panels/screencast/screencastView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/screencast/screencastView.css');
     this._shortcuts = {} as {
       [x: number]: (arg0?: Event|undefined) => boolean,
     };
diff --git a/front_end/panels/search/SearchResultsPane.ts b/front_end/panels/search/SearchResultsPane.ts
index 3b78c92..f2868b9 100644
--- a/front_end/panels/search/SearchResultsPane.ts
+++ b/front_end/panels/search/SearchResultsPane.ts
@@ -46,7 +46,7 @@
     this._searchResults = [];
     this._treeOutline = new UI.TreeOutline.TreeOutlineInShadow();
     this._treeOutline.hideOverflow();
-    this._treeOutline.registerRequiredCSS('panels/search/searchResultsPane.css', {enableLegacyPatching: false});
+    this._treeOutline.registerRequiredCSS('panels/search/searchResultsPane.css');
     this.contentElement.appendChild(this._treeOutline.element);
 
     this._matchesExpandedCount = 0;
diff --git a/front_end/panels/search/SearchView.ts b/front_end/panels/search/SearchView.ts
index cddc6e6..0146f7a 100644
--- a/front_end/panels/search/SearchView.ts
+++ b/front_end/panels/search/SearchView.ts
@@ -111,7 +111,7 @@
   constructor(settingKey: string) {
     super(true);
     this.setMinimumSize(0, 40);
-    this.registerRequiredCSS('panels/search/searchView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/search/searchView.css');
 
     this._focusOnShow = false;
     this._isIndexing = false;
diff --git a/front_end/panels/security/SecurityPanel.ts b/front_end/panels/security/SecurityPanel.ts
index 379ffda..8ee946e 100644
--- a/front_end/panels/security/SecurityPanel.ts
+++ b/front_end/panels/security/SecurityPanel.ts
@@ -793,8 +793,8 @@
   _elementsByOrigin: Map<string, SecurityPanelSidebarTreeElement>;
   constructor(mainViewElement: SecurityPanelSidebarTreeElement, showOriginInPanel: (arg0: Origin) => void) {
     super();
-    this.registerRequiredCSS('panels/security/sidebar.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('panels/security/lockIcon.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/security/sidebar.css');
+    this.registerRequiredCSS('panels/security/lockIcon.css');
     this.appendChild(mainViewElement);
 
     this._showOriginInPanel = showOriginInPanel;
@@ -976,8 +976,8 @@
   _securityState: Protocol.Security.SecurityState|null;
   constructor(panel: SecurityPanel) {
     super(true);
-    this.registerRequiredCSS('panels/security/mainView.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('panels/security/lockIcon.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/security/mainView.css');
+    this.registerRequiredCSS('panels/security/lockIcon.css');
     this.setMinimumSize(200, 100);
 
     this.contentElement.classList.add('security-main-view');
@@ -1467,8 +1467,8 @@
     this.setMinimumSize(200, 100);
 
     this.element.classList.add('security-origin-view');
-    this.registerRequiredCSS('panels/security/originView.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('panels/security/lockIcon.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/security/originView.css');
+    this.registerRequiredCSS('panels/security/lockIcon.css');
 
     const titleSection = this.element.createChild('div', 'title-section');
     const titleDiv = titleSection.createChild('div', 'title-section-header');
diff --git a/front_end/panels/settings/FrameworkIgnoreListSettingsTab.ts b/front_end/panels/settings/FrameworkIgnoreListSettingsTab.ts
index 2e62464..cc8301b 100644
--- a/front_end/panels/settings/FrameworkIgnoreListSettingsTab.ts
+++ b/front_end/panels/settings/FrameworkIgnoreListSettingsTab.ts
@@ -86,7 +86,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/settings/frameworkIgnoreListSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/settings/frameworkIgnoreListSettingsTab.css');
 
     const header = this.contentElement.createChild('div', 'header');
     header.textContent = i18nString(UIStrings.frameworkIgnoreList);
@@ -104,7 +104,7 @@
 
     this._list = new UI.ListWidget.ListWidget(this);
     this._list.element.classList.add('ignore-list');
-    this._list.registerRequiredCSS('panels/settings/frameworkIgnoreListSettingsTab.css', {enableLegacyPatching: false});
+    this._list.registerRequiredCSS('panels/settings/frameworkIgnoreListSettingsTab.css');
 
     const placeholder = document.createElement('div');
     placeholder.classList.add('ignore-list-empty');
diff --git a/front_end/panels/settings/KeybindsSettingsTab.ts b/front_end/panels/settings/KeybindsSettingsTab.ts
index 6e62a15..02567f2 100644
--- a/front_end/panels/settings/KeybindsSettingsTab.ts
+++ b/front_end/panels/settings/KeybindsSettingsTab.ts
@@ -85,7 +85,7 @@
   _editingRow: ShortcutListItem|null;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/settings/keybindsSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/settings/keybindsSettingsTab.css');
 
     const header = this.contentElement.createChild('header');
     header.createChild('h1').textContent = i18nString(UIStrings.shortcuts);
@@ -104,7 +104,7 @@
     this._list = new UI.ListControl.ListControl(this._items, this, UI.ListControl.ListMode.NonViewport);
     this._items.replaceAll(this._createListItems());
     UI.ARIAUtils.markAsList(this._list.element);
-    this.registerRequiredCSS('panels/settings/keybindsSettingsTab.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/settings/keybindsSettingsTab.css');
     this.contentElement.appendChild(this._list.element);
     UI.ARIAUtils.setAccessibleName(this._list.element, i18nString(UIStrings.keyboardShortcutsList));
     const footer = this.contentElement.createChild('div');
diff --git a/front_end/panels/settings/SettingsScreen.ts b/front_end/panels/settings/SettingsScreen.ts
index 68272ab..57afd6a 100644
--- a/front_end/panels/settings/SettingsScreen.ts
+++ b/front_end/panels/settings/SettingsScreen.ts
@@ -104,7 +104,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/settings/settingsScreen.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/settings/settingsScreen.css');
 
     this.contentElement.classList.add('settings-window-main');
     this.contentElement.classList.add('vbox');
@@ -113,8 +113,7 @@
     const settingsTitleElement =
         UI.Utils
             .createShadowRootWithCoreStyles(
-                settingsLabelElement,
-                {cssFile: 'panels/settings/settingsScreen.css', enableLegacyPatching: false, delegatesFocus: undefined})
+                settingsLabelElement, {cssFile: 'panels/settings/settingsScreen.css', delegatesFocus: undefined})
             .createChild('div', 'settings-window-title');
 
     UI.ARIAUtils.markAsHeading(settingsTitleElement, 1);
diff --git a/front_end/panels/sources/AddSourceMapURLDialog.ts b/front_end/panels/sources/AddSourceMapURLDialog.ts
index eda30d9..8a01060 100644
--- a/front_end/panels/sources/AddSourceMapURLDialog.ts
+++ b/front_end/panels/sources/AddSourceMapURLDialog.ts
@@ -25,7 +25,7 @@
   _callback: (arg0: string) => void;
   constructor(callback: (arg0: string) => void) {
     super(/* isWebComponent */ true);
-    this.registerRequiredCSS('panels/sources/dialog.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/dialog.css');
     this.contentElement.createChild('label').textContent = i18nString(UIStrings.sourceMapUrl);
 
     this._input = UI.UIUtils.createInput('add-source-map', 'text');
diff --git a/front_end/panels/sources/BreakpointEditDialog.ts b/front_end/panels/sources/BreakpointEditDialog.ts
index 88653b3..4dfc4b2 100644
--- a/front_end/panels/sources/BreakpointEditDialog.ts
+++ b/front_end/panels/sources/BreakpointEditDialog.ts
@@ -62,7 +62,7 @@
                                                                                          condition: string,
                                                                                        }) => Promise<void>) {
     super(true);
-    this.registerRequiredCSS('panels/sources/breakpointEditDialog.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/breakpointEditDialog.css');
     this._onFinish = onFinish;
     this._finished = false;
     this._editor = null;
diff --git a/front_end/panels/sources/CallStackSidebarPane.ts b/front_end/panels/sources/CallStackSidebarPane.ts
index 86f9646..18905c1 100644
--- a/front_end/panels/sources/CallStackSidebarPane.ts
+++ b/front_end/panels/sources/CallStackSidebarPane.ts
@@ -104,7 +104,7 @@
 
   private constructor() {
     super(i18nString(UIStrings.callStack), true);
-    this.registerRequiredCSS('panels/sources/callStackSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/callStackSidebarPane.css');
 
     this._ignoreListMessageElement = this._createIgnoreListMessageElement();
     this.contentElement.appendChild(this._ignoreListMessageElement);
diff --git a/front_end/panels/sources/DebuggerPausedMessage.ts b/front_end/panels/sources/DebuggerPausedMessage.ts
index 094a190..f78a22f 100644
--- a/front_end/panels/sources/DebuggerPausedMessage.ts
+++ b/front_end/panels/sources/DebuggerPausedMessage.ts
@@ -108,8 +108,7 @@
     this._element.classList.add('paused-message');
     this._element.classList.add('flex-none');
     const root = UI.Utils.createShadowRootWithCoreStyles(
-        this._element,
-        {cssFile: 'panels/sources/debuggerPausedMessage.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        this._element, {cssFile: 'panels/sources/debuggerPausedMessage.css', delegatesFocus: undefined});
     this._contentElement = (root.createChild('div') as HTMLElement);
     UI.ARIAUtils.markAsPoliteLiveRegion(this._element, false);
   }
diff --git a/front_end/panels/sources/JavaScriptBreakpointsSidebarPane.ts b/front_end/panels/sources/JavaScriptBreakpointsSidebarPane.ts
index b8cf142..735ac72 100644
--- a/front_end/panels/sources/JavaScriptBreakpointsSidebarPane.ts
+++ b/front_end/panels/sources/JavaScriptBreakpointsSidebarPane.ts
@@ -93,7 +93,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/sources/javaScriptBreakpointsSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/javaScriptBreakpointsSidebarPane.css');
 
     this._breakpointManager = Bindings.BreakpointManager.BreakpointManager.instance();
     this._breakpointManager.addEventListener(Bindings.BreakpointManager.Events.BreakpointAdded, this.update, this);
diff --git a/front_end/panels/sources/NavigatorView.ts b/front_end/panels/sources/NavigatorView.ts
index cb2023d..29541e6 100644
--- a/front_end/panels/sources/NavigatorView.ts
+++ b/front_end/panels/sources/NavigatorView.ts
@@ -158,11 +158,11 @@
   _groupByFolder?: any;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/sources/navigatorView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/navigatorView.css');
 
     this._placeholder = null;
     this._scriptsTree = new UI.TreeOutline.TreeOutlineInShadow();
-    this._scriptsTree.registerRequiredCSS('panels/sources/navigatorTree.css', {enableLegacyPatching: false});
+    this._scriptsTree.registerRequiredCSS('panels/sources/navigatorTree.css');
     this._scriptsTree.setComparator(NavigatorView._treeElementsCompare);
     this._scriptsTree.setFocusable(false);
     this.contentElement.appendChild(this._scriptsTree.element);
diff --git a/front_end/panels/sources/ScopeChainSidebarPane.ts b/front_end/panels/sources/ScopeChainSidebarPane.ts
index 034dd5c..fd0f05e 100644
--- a/front_end/panels/sources/ScopeChainSidebarPane.ts
+++ b/front_end/panels/sources/ScopeChainSidebarPane.ts
@@ -93,9 +93,9 @@
   _infoElement: HTMLDivElement;
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/sources/scopeChainSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/scopeChainSidebarPane.css');
     this._treeOutline = new ObjectUI.ObjectPropertiesSection.ObjectPropertiesSectionsTreeOutline();
-    this._treeOutline.registerRequiredCSS('panels/sources/scopeChainSidebarPane.css', {enableLegacyPatching: false});
+    this._treeOutline.registerRequiredCSS('panels/sources/scopeChainSidebarPane.css');
     this._treeOutline.setShowSelectionOnKeyboardFocus(/* show */ true);
     this._expandController =
         new ObjectUI.ObjectPropertiesSection.ObjectPropertiesSectionsTreeExpandController(this._treeOutline);
diff --git a/front_end/panels/sources/SourcesPanel.ts b/front_end/panels/sources/SourcesPanel.ts
index ab70efd..63b40ff 100644
--- a/front_end/panels/sources/SourcesPanel.ts
+++ b/front_end/panels/sources/SourcesPanel.ts
@@ -189,7 +189,7 @@
   sidebarPaneView?: UI.Widget.VBox|UI.SplitWidget.SplitWidget;
   constructor() {
     super('sources');
-    this.registerRequiredCSS('panels/sources/sourcesPanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/sourcesPanel.css');
     new UI.DropTarget.DropTarget(
         this.element, [UI.DropTarget.Type.Folder], i18nString(UIStrings.dropWorkspaceFolderHere),
         this._handleDrop.bind(this));
diff --git a/front_end/panels/sources/SourcesView.ts b/front_end/panels/sources/SourcesView.ts
index de4c177..e5e6df6 100644
--- a/front_end/panels/sources/SourcesView.ts
+++ b/front_end/panels/sources/SourcesView.ts
@@ -62,7 +62,7 @@
 
   constructor() {
     super();
-    this.registerRequiredCSS('panels/sources/sourcesView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/sourcesView.css');
     this.element.id = 'sources-panel-sources-view';
     this.setMinimumAndPreferredSizes(250, 52, 250, 100);
 
diff --git a/front_end/panels/sources/ThreadsSidebarPane.ts b/front_end/panels/sources/ThreadsSidebarPane.ts
index c78891c..9cf3213 100644
--- a/front_end/panels/sources/ThreadsSidebarPane.ts
+++ b/front_end/panels/sources/ThreadsSidebarPane.ts
@@ -28,7 +28,7 @@
 
   private constructor() {
     super(true);
-    this.registerRequiredCSS('panels/sources/threadsSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/sources/threadsSidebarPane.css');
 
     this._items = new UI.ListModel.ListModel();
     this._list = new UI.ListControl.ListControl(this._items, this, UI.ListControl.ListMode.NonViewport);
diff --git a/front_end/panels/sources/UISourceCodeFrame.ts b/front_end/panels/sources/UISourceCodeFrame.ts
index 8871ce2..477596c 100644
--- a/front_end/panels/sources/UISourceCodeFrame.ts
+++ b/front_end/panels/sources/UISourceCodeFrame.ts
@@ -744,9 +744,7 @@
 
   _messageDescription(levels: Set<Workspace.UISourceCode.Message.Level>): Element {
     this._messagesDescriptionElement.removeChildren();
-    UI.Utils.appendStyle(
-        this._messagesDescriptionElement, 'ui/legacy/components/source_frame/messagesPopover.css',
-        {enableLegacyPatching: false});
+    UI.Utils.appendStyle(this._messagesDescriptionElement, 'ui/legacy/components/source_frame/messagesPopover.css');
     for (const message of this._messages.filter(m => levels.has(m.getMessage().level()))) {
       this._messagesDescriptionElement.append(message.element);
     }
diff --git a/front_end/panels/sources/WatchExpressionsSidebarPane.ts b/front_end/panels/sources/WatchExpressionsSidebarPane.ts
index a5be52a..caed8b25 100644
--- a/front_end/panels/sources/WatchExpressionsSidebarPane.ts
+++ b/front_end/panels/sources/WatchExpressionsSidebarPane.ts
@@ -98,8 +98,8 @@
   _linkifier: Components.Linkifier.Linkifier;
   private constructor() {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('panels/sources/watchExpressionsSidebarPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
+    this.registerRequiredCSS('panels/sources/watchExpressionsSidebarPane.css');
 
     // TODO(szuend): Replace with a Set once the web test
     // panels/sources/debugger-ui/watch-expressions-preserve-expansion.js is either converted
@@ -118,8 +118,7 @@
     this.contentElement.classList.add('watch-expressions');
     this.contentElement.addEventListener('contextmenu', this._contextMenu.bind(this), false);
     this._treeOutline = new ObjectUI.ObjectPropertiesSection.ObjectPropertiesSectionsTreeOutline();
-    this._treeOutline.registerRequiredCSS(
-        'panels/sources/watchExpressionsSidebarPane.css', {enableLegacyPatching: false});
+    this._treeOutline.registerRequiredCSS('panels/sources/watchExpressionsSidebarPane.css');
     this._treeOutline.setShowSelectionOnKeyboardFocus(/* show */ true);
     this._expandController =
         new ObjectUI.ObjectPropertiesSection.ObjectPropertiesSectionsTreeExpandController(this._treeOutline);
diff --git a/front_end/panels/timeline/TimelineFlameChartDataProvider.ts b/front_end/panels/timeline/TimelineFlameChartDataProvider.ts
index 5800aad..a3eea18 100644
--- a/front_end/panels/timeline/TimelineFlameChartDataProvider.ts
+++ b/front_end/panels/timeline/TimelineFlameChartDataProvider.ts
@@ -1036,7 +1036,6 @@
     const element = document.createElement('div');
     const root = UI.Utils.createShadowRootWithCoreStyles(element, {
       cssFile: 'panels/timeline/timelineFlamechartPopover.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     const contents = root.createChild('div', 'timeline-flamechart-popover');
diff --git a/front_end/panels/timeline/TimelineFlameChartNetworkDataProvider.ts b/front_end/panels/timeline/TimelineFlameChartNetworkDataProvider.ts
index dae4d0e..bef26a6 100644
--- a/front_end/panels/timeline/TimelineFlameChartNetworkDataProvider.ts
+++ b/front_end/panels/timeline/TimelineFlameChartNetworkDataProvider.ts
@@ -294,7 +294,6 @@
     const element = document.createElement('div');
     const root = UI.Utils.createShadowRootWithCoreStyles(element, {
       cssFile: 'panels/timeline/timelineFlamechartPopover.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     const contents = root.createChild('div', 'timeline-flamechart-popover');
diff --git a/front_end/panels/timeline/TimelineHistoryManager.ts b/front_end/panels/timeline/TimelineHistoryManager.ts
index 3a77942..e2624f1 100644
--- a/front_end/panels/timeline/TimelineHistoryManager.ts
+++ b/front_end/panels/timeline/TimelineHistoryManager.ts
@@ -335,7 +335,6 @@
 
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(this._glassPane.contentElement, {
       cssFile: 'panels/timeline/timelineHistoryManager.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     const contentElement = shadowRoot.createChild('div', 'drop-down');
@@ -468,7 +467,7 @@
     const element = document.createElement('button');
     element.classList.add('history-dropdown-button');
     super(element);
-    UI.Utils.appendStyle(this.element, 'panels/timeline/historyToolbarButton.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(this.element, 'panels/timeline/historyToolbarButton.css');
     this._contentElement = this.element.createChild('span', 'content');
     const dropdownArrowIcon = UI.Icon.Icon.create('smallicon-triangle-down');
     this.element.appendChild(dropdownArrowIcon);
diff --git a/front_end/panels/timeline/TimelinePaintProfilerView.ts b/front_end/panels/timeline/TimelinePaintProfilerView.ts
index 8f3a8f2..49ae070 100644
--- a/front_end/panels/timeline/TimelinePaintProfilerView.ts
+++ b/front_end/panels/timeline/TimelinePaintProfilerView.ts
@@ -156,7 +156,7 @@
   _maskRectangle?: Protocol.DOM.Rect|null;
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/timeline/timelinePaintProfiler.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/timeline/timelinePaintProfiler.css');
     this.contentElement.classList.add('fill', 'paint-profiler-image-view');
     this._imageContainer = this.contentElement.createChild('div', 'paint-profiler-image-container');
     this._imageElement = (this._imageContainer.createChild('img') as HTMLImageElement);
diff --git a/front_end/panels/timeline/TimelinePanel.ts b/front_end/panels/timeline/TimelinePanel.ts
index 0068347..5e35941 100644
--- a/front_end/panels/timeline/TimelinePanel.ts
+++ b/front_end/panels/timeline/TimelinePanel.ts
@@ -315,7 +315,7 @@
   _selection?: TimelineSelection|null;
   constructor() {
     super('timeline');
-    this.registerRequiredCSS('panels/timeline/timelinePanel.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/timeline/timelinePanel.css');
     this.element.addEventListener('contextmenu', this._contextMenu.bind(this), false);
     this._dropTarget = new UI.DropTarget.DropTarget(
         this.element, [UI.DropTarget.Type.File, UI.DropTarget.Type.URI],
@@ -1357,7 +1357,7 @@
       },
       buttonCallback: () => (Promise<void>| void)) {
     super(true);
-    this.registerRequiredCSS('panels/timeline/timelineStatusDialog.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/timeline/timelineStatusDialog.css');
     this.contentElement.classList.add('timeline-status-dialog');
 
     const statusLine = this.contentElement.createChild('div', 'status-dialog-line status');
diff --git a/front_end/panels/timeline/TimelineUIUtils.ts b/front_end/panels/timeline/TimelineUIUtils.ts
index 512147b..02c1cd8 100644
--- a/front_end/panels/timeline/TimelineUIUtils.ts
+++ b/front_end/panels/timeline/TimelineUIUtils.ts
@@ -2806,8 +2806,7 @@
     }
 
     const invalidationsTreeOutline = new UI.TreeOutline.TreeOutlineInShadow();
-    invalidationsTreeOutline.registerRequiredCSS(
-        'panels/timeline/invalidationsTree.css', {enableLegacyPatching: false});
+    invalidationsTreeOutline.registerRequiredCSS('panels/timeline/invalidationsTree.css');
     invalidationsTreeOutline.element.classList.add('invalidations-tree');
 
     const invalidationGroups = groupInvalidationsByCause(invalidations);
@@ -2915,7 +2914,7 @@
       return null;
     }
     const container = document.createElement('div');
-    UI.Utils.appendStyle(container, 'ui/legacy/components/utils/imagePreview.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(container, 'ui/legacy/components/utils/imagePreview.css');
     container.classList.add('image-preview-container', 'vbox', 'link');
     const img = (container.createChild('img') as HTMLImageElement);
     img.src = imageURL;
diff --git a/front_end/panels/web_audio/AudioContextSelector.ts b/front_end/panels/web_audio/AudioContextSelector.ts
index 86d799f..3d0abcd 100644
--- a/front_end/panels/web_audio/AudioContextSelector.ts
+++ b/front_end/panels/web_audio/AudioContextSelector.ts
@@ -94,8 +94,7 @@
   createElementForItem(item: Protocol.WebAudio.BaseAudioContext): Element {
     const element = document.createElement('div');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-        element,
-        {cssFile: 'panels/web_audio/audioContextSelector.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        element, {cssFile: 'panels/web_audio/audioContextSelector.css', delegatesFocus: undefined});
     const title = shadowRoot.createChild('div', 'title');
     UI.UIUtils.createTextChild(title, Platform.StringUtilities.trimEndWithMaxLength(this.titleFor(item), 100));
     return element;
diff --git a/front_end/panels/web_audio/WebAudioView.ts b/front_end/panels/web_audio/WebAudioView.ts
index 27ffc52..d1338bf 100644
--- a/front_end/panels/web_audio/WebAudioView.ts
+++ b/front_end/panels/web_audio/WebAudioView.ts
@@ -36,7 +36,7 @@
   constructor() {
     super(true, 1000);
     this.element.classList.add('web-audio-drawer');
-    this.registerRequiredCSS('panels/web_audio/webAudio.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/web_audio/webAudio.css');
 
     // Creates the toolbar.
     const toolbarContainer = this.contentElement.createChild('div', 'web-audio-toolbar-container vbox');
diff --git a/front_end/panels/webauthn/WebauthnPane.ts b/front_end/panels/webauthn/WebauthnPane.ts
index 3e7e907..8ec33cc 100644
--- a/front_end/panels/webauthn/WebauthnPane.ts
+++ b/front_end/panels/webauthn/WebauthnPane.ts
@@ -244,7 +244,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('panels/webauthn/webauthnPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('panels/webauthn/webauthnPane.css');
     this.contentElement.classList.add('webauthn-pane');
     this._enabled = false;
     this._activeAuthId = null;
diff --git a/front_end/ui/components/data_grid/DataGrid.ts b/front_end/ui/components/data_grid/DataGrid.ts
index e8bcc33..2191a03 100644
--- a/front_end/ui/components/data_grid/DataGrid.ts
+++ b/front_end/ui/components/data_grid/DataGrid.ts
@@ -168,8 +168,7 @@
   constructor() {
     super();
     this.shadow.adoptedStyleSheets = [
-      ...ComponentHelpers.GetStylesheet.getStyleSheets(
-          'ui/legacy/inspectorScrollbars.css', {enableLegacyPatching: false}),
+      ...ComponentHelpers.GetStylesheet.getStyleSheets('ui/legacy/inspectorScrollbars.css'),
     ];
   }
   connectedCallback(): void {
diff --git a/front_end/ui/components/helpers/get-stylesheet.ts b/front_end/ui/components/helpers/get-stylesheet.ts
index 29d6b22..6aae6e1 100644
--- a/front_end/ui/components/helpers/get-stylesheet.ts
+++ b/front_end/ui/components/helpers/get-stylesheet.ts
@@ -3,9 +3,8 @@
 // found in the LICENSE file.
 
 import * as Root from '../../../core/root/root.js';
-import * as ThemeSupport from '../../legacy/theme_support/theme_support.js';
 
-const sheetsCache = new Map<string, {sheets: CSSStyleSheet[], enableLegacyPatching: false}>();
+const sheetsCache = new Map<string, {sheets: CSSStyleSheet[]}>();
 
 /**
  * Helper for importing a legacy stylesheet into a component.
@@ -13,11 +12,9 @@
  * Given a path to a stylesheet, it returns a CSSStyleSheet that can then be
  * adopted by your component.
  */
-export function getStyleSheets(path: string, {enableLegacyPatching}: {enableLegacyPatching: false} = {
-  enableLegacyPatching: false,
-}): CSSStyleSheet[] {
+export function getStyleSheets(path: string): CSSStyleSheet[] {
   const cachedResult = sheetsCache.get(path);
-  if (cachedResult && cachedResult.enableLegacyPatching === enableLegacyPatching) {
+  if (cachedResult) {
     return cachedResult.sheets;
   }
 
@@ -25,22 +22,10 @@
   if (!content) {
     throw new Error(`${path} not preloaded.`);
   }
-
   const originalStylesheet = new CSSStyleSheet();
   originalStylesheet.replaceSync(content);
-
-  const themeStyleSheet = ThemeSupport.ThemeSupport.instance().themeStyleSheet(path, content);
-  if (!enableLegacyPatching || !themeStyleSheet) {
-    sheetsCache.set(path, {enableLegacyPatching, sheets: [originalStylesheet]});
-    return [originalStylesheet];
-  }
-
-  const patchedStyleSheet = new CSSStyleSheet();
-
-  patchedStyleSheet.replaceSync(themeStyleSheet + '\n' + Root.Runtime.Runtime.resolveSourceURL(path + '.theme'));
-  sheetsCache.set(path, {enableLegacyPatching, sheets: [originalStylesheet, patchedStyleSheet]});
-
-  return [originalStylesheet, patchedStyleSheet];
+  sheetsCache.set(path, {sheets: [originalStylesheet]});
+  return [originalStylesheet];
 }
 
 /*
diff --git a/front_end/ui/components/linear_memory_inspector/LinearMemoryValueInterpreter.ts b/front_end/ui/components/linear_memory_inspector/LinearMemoryValueInterpreter.ts
index 59f13ad..ce0a5dd 100644
--- a/front_end/ui/components/linear_memory_inspector/LinearMemoryValueInterpreter.ts
+++ b/front_end/ui/components/linear_memory_inspector/LinearMemoryValueInterpreter.ts
@@ -73,7 +73,7 @@
   constructor() {
     super();
     this.shadow.adoptedStyleSheets = [
-      ...getStyleSheets('ui/legacy/inspectorCommon.css', {enableLegacyPatching: false}),
+      ...getStyleSheets('ui/legacy/inspectorCommon.css'),
     ];
   }
 
diff --git a/front_end/ui/components/linear_memory_inspector/ValueInterpreterDisplay.ts b/front_end/ui/components/linear_memory_inspector/ValueInterpreterDisplay.ts
index 4ad6daf..5c43120 100644
--- a/front_end/ui/components/linear_memory_inspector/ValueInterpreterDisplay.ts
+++ b/front_end/ui/components/linear_memory_inspector/ValueInterpreterDisplay.ts
@@ -83,7 +83,7 @@
   constructor() {
     super();
     this.shadow.adoptedStyleSheets = [
-      ...getStyleSheets('ui/legacy/inspectorCommon.css', {enableLegacyPatching: false}),
+      ...getStyleSheets('ui/legacy/inspectorCommon.css'),
     ];
   }
 
diff --git a/front_end/ui/legacy/Dialog.ts b/front_end/ui/legacy/Dialog.ts
index da1d51a..9f72dd1 100644
--- a/front_end/ui/legacy/Dialog.ts
+++ b/front_end/ui/legacy/Dialog.ts
@@ -50,7 +50,7 @@
 
   constructor() {
     super();
-    this.registerRequiredCSS('ui/legacy/dialog.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/dialog.css');
     this.contentElement.tabIndex = 0;
     this.contentElement.addEventListener('focus', () => this.widget().focus(), false);
     this.widget().setDefaultFocusedElement(this.contentElement);
diff --git a/front_end/ui/legacy/DropTarget.ts b/front_end/ui/legacy/DropTarget.ts
index 2cbe7bc..93764f5 100644
--- a/front_end/ui/legacy/DropTarget.ts
+++ b/front_end/ui/legacy/DropTarget.ts
@@ -73,8 +73,7 @@
     }
     this._dragMaskElement = this._element.createChild('div', '');
     const shadowRoot = createShadowRootWithCoreStyles(
-        this._dragMaskElement,
-        {cssFile: 'ui/legacy/dropTarget.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        this._dragMaskElement, {cssFile: 'ui/legacy/dropTarget.css', delegatesFocus: undefined});
     shadowRoot.createChild('div', 'drop-target-message').textContent = this._messageText;
     this._dragMaskElement.addEventListener('drop', this._onDrop.bind(this), true);
     this._dragMaskElement.addEventListener('dragleave', this._onDragLeave.bind(this), true);
diff --git a/front_end/ui/legacy/EmptyWidget.ts b/front_end/ui/legacy/EmptyWidget.ts
index 7014e51..15fbae8 100644
--- a/front_end/ui/legacy/EmptyWidget.ts
+++ b/front_end/ui/legacy/EmptyWidget.ts
@@ -50,7 +50,7 @@
 
   constructor(text: string) {
     super();
-    this.registerRequiredCSS('ui/legacy/emptyWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/emptyWidget.css');
     this.element.classList.add('empty-view-scroller');
     this._contentElement = this.element.createChild('div', 'empty-view');
     this._textElement = this._contentElement.createChild('div', 'empty-bold-text');
diff --git a/front_end/ui/legacy/FilterBar.ts b/front_end/ui/legacy/FilterBar.ts
index 39b91c7..c9c3499 100644
--- a/front_end/ui/legacy/FilterBar.ts
+++ b/front_end/ui/legacy/FilterBar.ts
@@ -77,7 +77,7 @@
 
   constructor(name: string, visibleByDefault?: boolean) {
     super();
-    this.registerRequiredCSS('ui/legacy/filter.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/filter.css');
     this._enabled = true;
     this.element.classList.add('filter-bar');
 
diff --git a/front_end/ui/legacy/GlassPane.ts b/front_end/ui/legacy/GlassPane.ts
index 946d803..d72ea7c 100644
--- a/front_end/ui/legacy/GlassPane.ts
+++ b/front_end/ui/legacy/GlassPane.ts
@@ -40,7 +40,7 @@
       this.element.shadowRoot.appendChild(this._arrowElement);
     }
 
-    this.registerRequiredCSS('ui/legacy/glassPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/glassPane.css');
     this.setPointerEventsBehavior(PointerEventsBehavior.PierceGlassPane);
 
     this._onMouseDownBound = this._onMouseDown.bind(this);
@@ -58,10 +58,8 @@
     return this._widget.isShowing();
   }
 
-  registerRequiredCSS(cssFile: string, options: {
-    enableLegacyPatching: false,
-  }): void {
-    this._widget.registerRequiredCSS(cssFile, options);
+  registerRequiredCSS(cssFile: string): void {
+    this._widget.registerRequiredCSS(cssFile);
   }
 
   setDefaultFocusedElement(element: Element|null): void {
diff --git a/front_end/ui/legacy/Infobar.ts b/front_end/ui/legacy/Infobar.ts
index 1f21c35..8d0cd9a 100644
--- a/front_end/ui/legacy/Infobar.ts
+++ b/front_end/ui/legacy/Infobar.ts
@@ -59,8 +59,8 @@
   constructor(type: Type, text: string, actions?: InfobarAction[], disableSetting?: Common.Settings.Setting<any>) {
     this.element = (document.createElement('div') as HTMLElement);
     this.element.classList.add('flex-none');
-    this._shadowRoot = createShadowRootWithCoreStyles(
-        this.element, {cssFile: 'ui/legacy/infobar.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    this._shadowRoot =
+        createShadowRootWithCoreStyles(this.element, {cssFile: 'ui/legacy/infobar.css', delegatesFocus: undefined});
 
     this._contentElement = this._shadowRoot.createChild('div', 'infobar infobar-' + type) as HTMLDivElement;
 
diff --git a/front_end/ui/legacy/InspectorView.ts b/front_end/ui/legacy/InspectorView.ts
index 587eb4f..45f69f2 100644
--- a/front_end/ui/legacy/InspectorView.ts
+++ b/front_end/ui/legacy/InspectorView.ts
@@ -156,7 +156,7 @@
 
     this._tabbedPane = this._tabbedLocation.tabbedPane();
     this._tabbedPane.element.classList.add('main-tabbed-pane');
-    this._tabbedPane.registerRequiredCSS('ui/legacy/inspectorViewTabbedPane.css', {enableLegacyPatching: false});
+    this._tabbedPane.registerRequiredCSS('ui/legacy/inspectorViewTabbedPane.css');
     this._tabbedPane.addEventListener(TabbedPaneEvents.TabSelected, this._tabSelected, this);
     this._tabbedPane.setAccessibleName(i18nString(UIStrings.panels));
     this._tabbedPane.setTabDelegate(this._tabDelegate);
diff --git a/front_end/ui/legacy/ListWidget.ts b/front_end/ui/legacy/ListWidget.ts
index 4367817..cc6d6fa 100644
--- a/front_end/ui/legacy/ListWidget.ts
+++ b/front_end/ui/legacy/ListWidget.ts
@@ -51,7 +51,7 @@
   _emptyPlaceholder: Element|null;
   constructor(delegate: Delegate<T>, delegatesFocus: boolean|undefined = true) {
     super(true, delegatesFocus);
-    this.registerRequiredCSS('ui/legacy/listWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/listWidget.css');
     this._delegate = delegate;
 
     this._list = this.contentElement.createChild('div', 'list');
diff --git a/front_end/ui/legacy/PopoverHelper.ts b/front_end/ui/legacy/PopoverHelper.ts
index 374ff1b..734534d 100644
--- a/front_end/ui/legacy/PopoverHelper.ts
+++ b/front_end/ui/legacy/PopoverHelper.ts
@@ -191,7 +191,7 @@
 
   _showPopover(document: Document): void {
     const popover = new GlassPane();
-    popover.registerRequiredCSS('ui/legacy/popover.css', {enableLegacyPatching: false});
+    popover.registerRequiredCSS('ui/legacy/popover.css');
     popover.setSizeBehavior(SizeBehavior.MeasureContent);
     popover.setMarginBehavior(MarginBehavior.Arrow);
     const request = this._scheduledRequest;
diff --git a/front_end/ui/legacy/ProgressIndicator.ts b/front_end/ui/legacy/ProgressIndicator.ts
index 92265a2..7c48450 100644
--- a/front_end/ui/legacy/ProgressIndicator.ts
+++ b/front_end/ui/legacy/ProgressIndicator.ts
@@ -48,8 +48,7 @@
     this.element = document.createElement('div');
     this.element.classList.add('progress-indicator');
     this._shadowRoot = createShadowRootWithCoreStyles(
-        this.element,
-        {cssFile: 'ui/legacy/progressIndicator.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        this.element, {cssFile: 'ui/legacy/progressIndicator.css', delegatesFocus: undefined});
     this._contentElement = this._shadowRoot.createChild('div', 'progress-indicator-shadow-container');
 
     this._labelElement = this._contentElement.createChild('div', 'title');
diff --git a/front_end/ui/legacy/RemoteDebuggingTerminatedScreen.ts b/front_end/ui/legacy/RemoteDebuggingTerminatedScreen.ts
index 29e9ef1..c336894 100644
--- a/front_end/ui/legacy/RemoteDebuggingTerminatedScreen.ts
+++ b/front_end/ui/legacy/RemoteDebuggingTerminatedScreen.ts
@@ -32,7 +32,7 @@
 export class RemoteDebuggingTerminatedScreen extends VBox {
   constructor(reason: string) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/remoteDebuggingTerminatedScreen.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/remoteDebuggingTerminatedScreen.css');
     const message = this.contentElement.createChild('div', 'message');
     const reasonElement = message.createChild('span', 'reason');
     reasonElement.textContent = reason;
diff --git a/front_end/ui/legacy/ReportView.ts b/front_end/ui/legacy/ReportView.ts
index 98f4631..d6004f3 100644
--- a/front_end/ui/legacy/ReportView.ts
+++ b/front_end/ui/legacy/ReportView.ts
@@ -22,7 +22,7 @@
   _urlElement?: HTMLElement;
   constructor(title?: string) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/reportView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/reportView.css');
 
     this._contentBox = this.contentElement.createChild('div', 'report-content-box');
     this._headerElement = this._contentBox.createChild('div', 'report-header vbox');
diff --git a/front_end/ui/legacy/RootView.ts b/front_end/ui/legacy/RootView.ts
index 112fd52..1ad72f4 100644
--- a/front_end/ui/legacy/RootView.ts
+++ b/front_end/ui/legacy/RootView.ts
@@ -13,7 +13,7 @@
     super();
     this.markAsRoot();
     this.element.classList.add('root-view');
-    this.registerRequiredCSS('ui/legacy/rootView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/rootView.css');
     this.element.setAttribute('spellcheck', 'false');
   }
 
diff --git a/front_end/ui/legacy/SearchableView.ts b/front_end/ui/legacy/SearchableView.ts
index d60865b..77e87b4 100644
--- a/front_end/ui/legacy/SearchableView.ts
+++ b/front_end/ui/legacy/SearchableView.ts
@@ -125,7 +125,7 @@
 
   constructor(searchable: Searchable, replaceable: Replaceable|null, settingName?: string) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/searchableView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/searchableView.css');
     searchableViewsByElement.set(this.element, this);
 
     this._searchProvider = searchable;
diff --git a/front_end/ui/legacy/SoftContextMenu.ts b/front_end/ui/legacy/SoftContextMenu.ts
index be8a871..73e06ee 100644
--- a/front_end/ui/legacy/SoftContextMenu.ts
+++ b/front_end/ui/legacy/SoftContextMenu.ts
@@ -100,7 +100,7 @@
     this._glassPane = new GlassPane();
     this._glassPane.setPointerEventsBehavior(
         this._parentMenu ? PointerEventsBehavior.PierceGlassPane : PointerEventsBehavior.BlockedByGlassPane);
-    this._glassPane.registerRequiredCSS('ui/legacy/softContextMenu.css', {enableLegacyPatching: false});
+    this._glassPane.registerRequiredCSS('ui/legacy/softContextMenu.css');
     this._glassPane.setContentAnchorBox(anchorBox);
     this._glassPane.setSizeBehavior(SizeBehavior.MeasureContent);
     this._glassPane.setMarginBehavior(MarginBehavior.NoMargin);
diff --git a/front_end/ui/legacy/SoftDropDown.ts b/front_end/ui/legacy/SoftDropDown.ts
index dffa887..84512bc 100644
--- a/front_end/ui/legacy/SoftDropDown.ts
+++ b/front_end/ui/legacy/SoftDropDown.ts
@@ -49,7 +49,7 @@
 
     this.element = document.createElement('button');
     this.element.classList.add('soft-dropdown');
-    appendStyle(this.element, 'ui/legacy/softDropDownButton.css', {enableLegacyPatching: false});
+    appendStyle(this.element, 'ui/legacy/softDropDownButton.css');
     this._titleElement = this.element.createChild('span', 'title');
     const dropdownArrowIcon = Icon.create('smallicon-triangle-down');
     this.element.appendChild(dropdownArrowIcon);
@@ -66,7 +66,6 @@
     this._width = 315;
     createShadowRootWithCoreStyles(this._glassPane.contentElement, {
       cssFile: 'ui/legacy/softDropDown.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     }).appendChild(this._list.element);
     ARIAUtils.markAsMenu(this._list.element);
diff --git a/front_end/ui/legacy/SplitWidget.ts b/front_end/ui/legacy/SplitWidget.ts
index 70fb692..07e35ff 100644
--- a/front_end/ui/legacy/SplitWidget.ts
+++ b/front_end/ui/legacy/SplitWidget.ts
@@ -78,7 +78,7 @@
       defaultSidebarHeight?: number, constraintsInDip?: boolean) {
     super(true);
     this.element.classList.add('split-widget');
-    this.registerRequiredCSS('ui/legacy/splitWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/splitWidget.css');
 
     this.contentElement.classList.add('shadow-split-widget');
     this._sidebarElement =
diff --git a/front_end/ui/legacy/SuggestBox.ts b/front_end/ui/legacy/SuggestBox.ts
index 5be0b82..444a8c0 100644
--- a/front_end/ui/legacy/SuggestBox.ts
+++ b/front_end/ui/legacy/SuggestBox.ts
@@ -110,8 +110,7 @@
     this._glassPane.setAnchorBehavior(AnchorBehavior.PreferBottom);
     this._glassPane.setOutsideClickCallback(this.hide.bind(this));
     const shadowRoot = createShadowRootWithCoreStyles(
-        this._glassPane.contentElement,
-        {cssFile: 'ui/legacy/suggestBox.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        this._glassPane.contentElement, {cssFile: 'ui/legacy/suggestBox.css', delegatesFocus: undefined});
     shadowRoot.appendChild(this._element);
   }
 
diff --git a/front_end/ui/legacy/TabbedPane.ts b/front_end/ui/legacy/TabbedPane.ts
index 022a668..6ac35b5 100644
--- a/front_end/ui/legacy/TabbedPane.ts
+++ b/front_end/ui/legacy/TabbedPane.ts
@@ -107,7 +107,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('ui/legacy/tabbedPane.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/tabbedPane.css');
     this.element.classList.add('tabbed-pane');
     this.contentElement.classList.add('tabbed-pane-shadow');
     this.contentElement.tabIndex = -1;
diff --git a/front_end/ui/legacy/TargetCrashedScreen.ts b/front_end/ui/legacy/TargetCrashedScreen.ts
index ba6dd74..233b126 100644
--- a/front_end/ui/legacy/TargetCrashedScreen.ts
+++ b/front_end/ui/legacy/TargetCrashedScreen.ts
@@ -24,7 +24,7 @@
   _hideCallback: () => void;
   constructor(hideCallback: () => void) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/targetCrashedScreen.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/targetCrashedScreen.css');
     this.contentElement.createChild('div', 'message').textContent =
         i18nString(UIStrings.devtoolsWasDisconnectedFromThe);
     this.contentElement.createChild('div', 'message').textContent =
diff --git a/front_end/ui/legacy/TextPrompt.ts b/front_end/ui/legacy/TextPrompt.ts
index 7c00b30..b294a80 100644
--- a/front_end/ui/legacy/TextPrompt.ts
+++ b/front_end/ui/legacy/TextPrompt.ts
@@ -136,7 +136,7 @@
     this._boundOnMouseWheel = this.onMouseWheel.bind(this);
     this._boundClearAutocomplete = this.clearAutocomplete.bind(this);
     this._proxyElement = element.ownerDocument.createElement('span');
-    appendStyle(this._proxyElement, 'ui/legacy/textPrompt.css', {enableLegacyPatching: false});
+    appendStyle(this._proxyElement, 'ui/legacy/textPrompt.css');
     this._contentElement = this._proxyElement.createChild('div', 'text-prompt-root');
     this._proxyElement.style.display = this._proxyElementDisplay;
     if (element.parentElement) {
diff --git a/front_end/ui/legacy/Toolbar.ts b/front_end/ui/legacy/Toolbar.ts
index 0615017..02cfa29 100644
--- a/front_end/ui/legacy/Toolbar.ts
+++ b/front_end/ui/legacy/Toolbar.ts
@@ -76,8 +76,8 @@
     this.element.className = className;
     this.element.classList.add('toolbar');
     this._enabled = true;
-    this._shadowRoot = createShadowRootWithCoreStyles(
-        this.element, {cssFile: 'ui/legacy/toolbar.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    this._shadowRoot =
+        createShadowRootWithCoreStyles(this.element, {cssFile: 'ui/legacy/toolbar.css', delegatesFocus: undefined});
     this._contentElement = this._shadowRoot.createChild('div', 'toolbar-shadow');
     this._insertionPoint = this._contentElement.createChild('slot');
   }
diff --git a/front_end/ui/legacy/Tooltip.ts b/front_end/ui/legacy/Tooltip.ts
index e1f9f2a..c97092c 100644
--- a/front_end/ui/legacy/Tooltip.ts
+++ b/front_end/ui/legacy/Tooltip.ts
@@ -22,8 +22,8 @@
 
   constructor(doc: Document) {
     this.element = doc.body.createChild('div');
-    this._shadowRoot = createShadowRootWithCoreStyles(
-        this.element, {cssFile: 'ui/legacy/tooltip.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    this._shadowRoot =
+        createShadowRootWithCoreStyles(this.element, {cssFile: 'ui/legacy/tooltip.css', delegatesFocus: undefined});
 
     this._tooltipElement = this._shadowRoot.createChild('div', 'tooltip') as HTMLDivElement;
     doc.addEventListener('mousemove', this._mouseMove.bind(this), true);
diff --git a/front_end/ui/legacy/Treeoutline.ts b/front_end/ui/legacy/Treeoutline.ts
index 28715ff..42e9d77 100644
--- a/front_end/ui/legacy/Treeoutline.ts
+++ b/front_end/ui/legacy/Treeoutline.ts
@@ -382,17 +382,15 @@
     super();
     this.contentElement.classList.add('tree-outline');
     this.element = (document.createElement('div') as HTMLElement);
-    this._shadowRoot = createShadowRootWithCoreStyles(
-        this.element, {cssFile: 'ui/legacy/treeoutline.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    this._shadowRoot =
+        createShadowRootWithCoreStyles(this.element, {cssFile: 'ui/legacy/treeoutline.css', delegatesFocus: undefined});
     this._disclosureElement = this._shadowRoot.createChild('div', 'tree-outline-disclosure');
     this._disclosureElement.appendChild(this.contentElement);
     this._renderSelection = true;
   }
 
-  registerRequiredCSS(cssFile: string, options: {
-    enableLegacyPatching: false,
-  }): void {
-    appendStyle(this._shadowRoot, cssFile, options);
+  registerRequiredCSS(cssFile: string): void {
+    appendStyle(this._shadowRoot, cssFile);
   }
 
   registerCSSFiles(cssFiles: CSSStyleSheet[]): void {
diff --git a/front_end/ui/legacy/UIUtils.ts b/front_end/ui/legacy/UIUtils.ts
index 1de0e93..920d16b 100644
--- a/front_end/ui/legacy/UIUtils.ts
+++ b/front_end/ui/legacy/UIUtils.ts
@@ -1217,8 +1217,8 @@
     super();
     CheckboxLabel._lastId = CheckboxLabel._lastId + 1;
     const id = 'ui-checkbox-label' + CheckboxLabel._lastId;
-    this._shadowRoot = createShadowRootWithCoreStyles(
-        this, {cssFile: 'ui/legacy/checkboxTextLabel.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    this._shadowRoot =
+        createShadowRootWithCoreStyles(this, {cssFile: 'ui/legacy/checkboxTextLabel.css', delegatesFocus: undefined});
     this.checkboxElement = (this._shadowRoot.createChild('input') as HTMLInputElement);
     this.checkboxElement.type = 'checkbox';
     this.checkboxElement.setAttribute('id', id);
@@ -1270,7 +1270,6 @@
   constructor() {
     super();
     const root = createShadowRootWithCoreStyles(this, {
-      enableLegacyPatching: false,
       cssFile: undefined,
       delegatesFocus: undefined,
     });
@@ -1300,8 +1299,8 @@
     this.radioElement.id = id;
     this.radioElement.type = 'radio';
     this.labelElement.htmlFor = id;
-    const root = createShadowRootWithCoreStyles(
-        this, {cssFile: 'ui/legacy/radioButton.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    const root =
+        createShadowRootWithCoreStyles(this, {cssFile: 'ui/legacy/radioButton.css', delegatesFocus: undefined});
     root.createChild('slot');
     this.addEventListener('click', this.radioClickHandler.bind(this), false);
   }
@@ -1323,8 +1322,7 @@
 
   constructor() {
     super();
-    const root = createShadowRootWithCoreStyles(
-        this, {cssFile: 'ui/legacy/slider.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    const root = createShadowRootWithCoreStyles(this, {cssFile: 'ui/legacy/slider.css', delegatesFocus: undefined});
     this.sliderElement = document.createElement('input');
     this.sliderElement.classList.add('dt-range-input');
     this.sliderElement.type = 'range';
@@ -1347,8 +1345,8 @@
 
   constructor() {
     super();
-    const root = createShadowRootWithCoreStyles(
-        this, {cssFile: 'ui/legacy/smallBubble.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    const root =
+        createShadowRootWithCoreStyles(this, {cssFile: 'ui/legacy/smallBubble.css', delegatesFocus: undefined});
     this._textElement = root.createChild('div');
     this._textElement.className = 'info';
     this._textElement.createChild('slot');
@@ -1368,8 +1366,8 @@
 
   constructor() {
     super();
-    const root = createShadowRootWithCoreStyles(
-        this, {cssFile: 'ui/legacy/closeButton.css', enableLegacyPatching: false, delegatesFocus: undefined});
+    const root =
+        createShadowRootWithCoreStyles(this, {cssFile: 'ui/legacy/closeButton.css', delegatesFocus: undefined});
     this._buttonElement = (root.createChild('div', 'close-button') as HTMLElement);
     ARIAUtils.setAccessibleName(this._buttonElement, i18nString(UIStrings.close));
     ARIAUtils.markAsButton(this._buttonElement);
@@ -1599,8 +1597,7 @@
     dialog.setSizeBehavior(SizeBehavior.MeasureContent);
     dialog.setDimmed(true);
     const shadowRoot = createShadowRootWithCoreStyles(
-        dialog.contentElement,
-        {cssFile: 'ui/legacy/confirmDialog.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        dialog.contentElement, {cssFile: 'ui/legacy/confirmDialog.css', delegatesFocus: undefined});
     const content = shadowRoot.createChild('div', 'widget');
     await new Promise(resolve => {
       const okButton = createTextButton(i18nString(UIStrings.ok), resolve, '', true);
@@ -1624,8 +1621,7 @@
     dialog.setDimmed(true);
     ARIAUtils.setAccessibleName(dialog.contentElement, message);
     const shadowRoot = createShadowRootWithCoreStyles(
-        dialog.contentElement,
-        {cssFile: 'ui/legacy/confirmDialog.css', enableLegacyPatching: false, delegatesFocus: undefined});
+        dialog.contentElement, {cssFile: 'ui/legacy/confirmDialog.css', delegatesFocus: undefined});
     const content = shadowRoot.createChild('div', 'widget');
     content.createChild('div', 'message').createChild('span').textContent = message;
     const buttonsBar = content.createChild('div', 'button');
@@ -1649,8 +1645,8 @@
 
 export function createInlineButton(toolbarButton: ToolbarButton): Element {
   const element = document.createElement('span');
-  const shadowRoot = createShadowRootWithCoreStyles(
-      element, {cssFile: 'ui/legacy/inlineButton.css', enableLegacyPatching: false, delegatesFocus: undefined});
+  const shadowRoot =
+      createShadowRootWithCoreStyles(element, {cssFile: 'ui/legacy/inlineButton.css', delegatesFocus: undefined});
   element.classList.add('inline-button');
   const toolbar = new Toolbar('');
   toolbar.appendToolbarItem(toolbarButton);
diff --git a/front_end/ui/legacy/ViewManager.ts b/front_end/ui/legacy/ViewManager.ts
index 1783e4a..6b2b317 100644
--- a/front_end/ui/legacy/ViewManager.ts
+++ b/front_end/ui/legacy/ViewManager.ts
@@ -410,7 +410,7 @@
   constructor(view: View) {
     super(true);
     this.element.classList.add('flex-none');
-    this.registerRequiredCSS('ui/legacy/viewContainers.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/viewContainers.css');
 
     this._titleElement = document.createElement('div');
     this._titleElement.classList.add('expandable-view-title');
diff --git a/front_end/ui/legacy/Widget.ts b/front_end/ui/legacy/Widget.ts
index 75409ed..55cee4f 100644
--- a/front_end/ui/legacy/Widget.ts
+++ b/front_end/ui/legacy/Widget.ts
@@ -81,7 +81,6 @@
       this.element.classList.add('flex-auto');
       this._shadowRoot = createShadowRootWithCoreStyles(this.element, {
         cssFile: undefined,
-        enableLegacyPatching: false,
         delegatesFocus,
       });
       this._shadowRoot.appendChild(this.contentElement);
@@ -464,13 +463,11 @@
     this.doResize();
   }
 
-  registerRequiredCSS(cssFile: string, options: {
-    enableLegacyPatching: false,
-  }): void {
+  registerRequiredCSS(cssFile: string): void {
     if (this._isWebComponent) {
-      appendStyle((this._shadowRoot as DocumentFragment), cssFile, options);
+      appendStyle((this._shadowRoot as DocumentFragment), cssFile);
     } else {
-      appendStyle(this.element, cssFile, options);
+      appendStyle(this.element, cssFile);
     }
   }
 
diff --git a/front_end/ui/legacy/XWidget.ts b/front_end/ui/legacy/XWidget.ts
index 0ab8d4f..c8ef36a 100644
--- a/front_end/ui/legacy/XWidget.ts
+++ b/front_end/ui/legacy/XWidget.ts
@@ -60,10 +60,8 @@
     return this._visible;
   }
 
-  registerRequiredCSS(cssFile: string, options: {
-    enableLegacyPatching: false,
-  }): void {
-    appendStyle(this._shadowRoot || this, cssFile, options);
+  registerRequiredCSS(cssFile: string): void {
+    appendStyle(this._shadowRoot || this, cssFile);
   }
 
   setOnShown(callback: (() => void)|null): void {
diff --git a/front_end/ui/legacy/components/color_picker/Spectrum.ts b/front_end/ui/legacy/components/color_picker/Spectrum.ts
index 59b72a6..4b67758 100644
--- a/front_end/ui/legacy/components/color_picker/Spectrum.ts
+++ b/front_end/ui/legacy/components/color_picker/Spectrum.ts
@@ -185,7 +185,7 @@
   _colorFormat?: string;
   constructor(contrastInfo?: ContrastInfo|null) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/color_picker/spectrum.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/color_picker/spectrum.css');
 
     this.contentElement.tabIndex = 0;
     this._colorElement = this.contentElement.createChild('div', 'spectrum-color');
diff --git a/front_end/ui/legacy/components/cookie_table/CookiesTable.ts b/front_end/ui/legacy/components/cookie_table/CookiesTable.ts
index 239682b..116606d 100644
--- a/front_end/ui/legacy/components/cookie_table/CookiesTable.ts
+++ b/front_end/ui/legacy/components/cookie_table/CookiesTable.ts
@@ -115,7 +115,7 @@
       deleteCallback?: ((arg0: SDK.Cookie.Cookie, arg1: () => void) => void)) {
     super();
 
-    this.registerRequiredCSS('ui/legacy/components/cookie_table/cookiesTable.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/cookie_table/cookiesTable.css');
     this.element.classList.add('cookies-table');
 
     this._saveCallback = saveCallback;
diff --git a/front_end/ui/legacy/components/data_grid/DataGrid.ts b/front_end/ui/legacy/components/data_grid/DataGrid.ts
index 9f19094..5d6871a 100644
--- a/front_end/ui/legacy/components/data_grid/DataGrid.ts
+++ b/front_end/ui/legacy/components/data_grid/DataGrid.ts
@@ -170,7 +170,7 @@
     const {displayName, columns: columnsArray, editCallback, deleteCallback, refreshCallback} = dataGridParameters;
     this.element = document.createElement('div');
     this.element.classList.add('data-grid');
-    UI.Utils.appendStyle(this.element, 'ui/legacy/components/data_grid/dataGrid.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(this.element, 'ui/legacy/components/data_grid/dataGrid.css');
     this.element.tabIndex = 0;
     this.element.addEventListener('keydown', this._keyDown.bind(this), false);
     this.element.addEventListener('contextmenu', this._contextMenu.bind(this), true);
diff --git a/front_end/ui/legacy/components/inline_editor/BezierEditor.ts b/front_end/ui/legacy/components/inline_editor/BezierEditor.ts
index 7a6eb8b..41cff19 100644
--- a/front_end/ui/legacy/components/inline_editor/BezierEditor.ts
+++ b/front_end/ui/legacy/components/inline_editor/BezierEditor.ts
@@ -30,7 +30,7 @@
   constructor(bezier: UI.Geometry.CubicBezier) {
     super(true);
     this._bezier = bezier;
-    this.registerRequiredCSS('ui/legacy/components/inline_editor/bezierEditor.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/inline_editor/bezierEditor.css');
     this.contentElement.tabIndex = 0;
     this.setDefaultFocusedElement(this.contentElement);
 
diff --git a/front_end/ui/legacy/components/inline_editor/CSSShadowEditor.ts b/front_end/ui/legacy/components/inline_editor/CSSShadowEditor.ts
index c589053..81d5475 100644
--- a/front_end/ui/legacy/components/inline_editor/CSSShadowEditor.ts
+++ b/front_end/ui/legacy/components/inline_editor/CSSShadowEditor.ts
@@ -61,7 +61,7 @@
   _changedElement?: HTMLInputElement|null;
   constructor() {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/inline_editor/cssShadowEditor.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/inline_editor/cssShadowEditor.css');
     this.contentElement.tabIndex = 0;
     this.setDefaultFocusedElement(this.contentElement);
 
diff --git a/front_end/ui/legacy/components/inline_editor/ColorSwatch.ts b/front_end/ui/legacy/components/inline_editor/ColorSwatch.ts
index fd9d799..cf81278 100644
--- a/front_end/ui/legacy/components/inline_editor/ColorSwatch.ts
+++ b/front_end/ui/legacy/components/inline_editor/ColorSwatch.ts
@@ -41,7 +41,7 @@
   constructor() {
     super();
     this.shadow.adoptedStyleSheets = [
-      ...getStyleSheets('ui/legacy/components/inline_editor/colorSwatch.css', {enableLegacyPatching: false}),
+      ...getStyleSheets('ui/legacy/components/inline_editor/colorSwatch.css'),
     ];
   }
 
diff --git a/front_end/ui/legacy/components/inline_editor/FontEditor.ts b/front_end/ui/legacy/components/inline_editor/FontEditor.ts
index d7e83c9..32b4e6f 100644
--- a/front_end/ui/legacy/components/inline_editor/FontEditor.ts
+++ b/front_end/ui/legacy/components/inline_editor/FontEditor.ts
@@ -124,7 +124,7 @@
 
   constructor(propertyMap: Map<string, string>) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/inline_editor/fontEditor.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/inline_editor/fontEditor.css');
     this._selectedNode = UI.Context.Context.instance().flavor(SDK.DOMModel.DOMNode);
 
     this._propertyMap = propertyMap;
diff --git a/front_end/ui/legacy/components/inline_editor/SwatchPopoverHelper.ts b/front_end/ui/legacy/components/inline_editor/SwatchPopoverHelper.ts
index 0dd35f3..a79349d 100644
--- a/front_end/ui/legacy/components/inline_editor/SwatchPopoverHelper.ts
+++ b/front_end/ui/legacy/components/inline_editor/SwatchPopoverHelper.ts
@@ -25,8 +25,7 @@
   constructor() {
     super();
     this._popover = new UI.GlassPane.GlassPane();
-    this._popover.registerRequiredCSS(
-        'ui/legacy/components/inline_editor/swatchPopover.css', {enableLegacyPatching: false});
+    this._popover.registerRequiredCSS('ui/legacy/components/inline_editor/swatchPopover.css');
     this._popover.setSizeBehavior(UI.GlassPane.SizeBehavior.MeasureContent);
     this._popover.setMarginBehavior(UI.GlassPane.MarginBehavior.Arrow);
     this._popover.element.addEventListener('mousedown', e => e.consume(), false);
diff --git a/front_end/ui/legacy/components/inline_editor/Swatches.ts b/front_end/ui/legacy/components/inline_editor/Swatches.ts
index 17d1230..4915512 100644
--- a/front_end/ui/legacy/components/inline_editor/Swatches.ts
+++ b/front_end/ui/legacy/components/inline_editor/Swatches.ts
@@ -19,7 +19,6 @@
     super();
     const root = UI.Utils.createShadowRootWithCoreStyles(this, {
       cssFile: 'ui/legacy/components/inline_editor/bezierSwatch.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     this._iconElement = UI.Icon.Icon.create('smallicon-bezier', 'bezier-swatch-icon');
@@ -67,7 +66,6 @@
     super();
     const root = UI.Utils.createShadowRootWithCoreStyles(this, {
       cssFile: 'ui/legacy/components/inline_editor/cssShadowSwatch.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     this._iconElement = UI.Icon.Icon.create('smallicon-shadow', 'shadow-swatch-icon');
diff --git a/front_end/ui/legacy/components/object_ui/CustomPreviewComponent.ts b/front_end/ui/legacy/components/object_ui/CustomPreviewComponent.ts
index 6524581..d0e0511 100644
--- a/front_end/ui/legacy/components/object_ui/CustomPreviewComponent.ts
+++ b/front_end/ui/legacy/components/object_ui/CustomPreviewComponent.ts
@@ -191,7 +191,6 @@
     this.element.classList.add('source-code');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(this.element, {
       cssFile: 'ui/legacy/components/object_ui/customPreviewComponent.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     this.element.addEventListener('contextmenu', this._contextMenuEventFired.bind(this), false);
diff --git a/front_end/ui/legacy/components/object_ui/ObjectPopoverHelper.ts b/front_end/ui/legacy/components/object_ui/ObjectPopoverHelper.ts
index 8396cbe..f6e19aa 100644
--- a/front_end/ui/legacy/components/object_ui/ObjectPopoverHelper.ts
+++ b/front_end/ui/legacy/components/object_ui/ObjectPopoverHelper.ts
@@ -74,8 +74,7 @@
       } else {
         popoverContentElement = document.createElement('div');
         popoverContentElement.classList.add('object-popover-content');
-        UI.Utils.appendStyle(
-            popoverContentElement, 'ui/legacy/components/object_ui/objectPopover.css', {enableLegacyPatching: false});
+        UI.Utils.appendStyle(popoverContentElement, 'ui/legacy/components/object_ui/objectPopover.css');
         const titleElement = popoverContentElement.createChild('div', 'monospace object-popover-title');
         titleElement.createChild('span').textContent = description;
         linkifier = new Components.Linkifier.Linkifier();
@@ -93,10 +92,8 @@
 
     popoverContentElement = document.createElement('span');
     popoverContentElement.dataset.stableNameForTest = 'object-popover-content';
-    UI.Utils.appendStyle(
-        popoverContentElement, 'ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
-    UI.Utils.appendStyle(
-        popoverContentElement, 'ui/legacy/components/object_ui/objectPopover.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(popoverContentElement, 'ui/legacy/components/object_ui/objectValue.css');
+    UI.Utils.appendStyle(popoverContentElement, 'ui/legacy/components/object_ui/objectPopover.css');
     const valueElement = popoverContentElement.createChild('span', 'monospace object-value-' + result.type);
     valueElement.style.whiteSpace = 'pre';
 
diff --git a/front_end/ui/legacy/components/object_ui/ObjectPropertiesSection.ts b/front_end/ui/legacy/components/object_ui/ObjectPropertiesSection.ts
index 1cfb3cd..2cc21f2 100644
--- a/front_end/ui/legacy/components/object_ui/ObjectPropertiesSection.ts
+++ b/front_end/ui/legacy/components/object_ui/ObjectPropertiesSection.ts
@@ -163,9 +163,8 @@
     }
 
     objectPropertiesSectionMap.set(this.element, this);
-    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS(
-        'ui/legacy/components/object_ui/objectPropertiesSection.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
+    this.registerRequiredCSS('ui/legacy/components/object_ui/objectPropertiesSection.css');
     this.rootElement().childrenListElement.classList.add('source-code', 'object-properties-section');
   }
 
@@ -187,7 +186,6 @@
     titleElement.classList.add('source-code');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(titleElement, {
       cssFile: 'ui/legacy/components/object_ui/objectValue.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     const propertyValue =
@@ -575,9 +573,8 @@
   _editable: boolean;
   constructor(options?: TreeOutlineOptions|null) {
     super();
-    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS(
-        'ui/legacy/components/object_ui/objectPropertiesSection.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/object_ui/objectValue.css');
+    this.registerRequiredCSS('ui/legacy/components/object_ui/objectPropertiesSection.css');
     this._editable = !(options && options.readOnly);
     this.contentElement.classList.add('source-code');
     this.contentElement.classList.add('object-properties-section');
diff --git a/front_end/ui/legacy/components/perf_ui/ChartViewport.ts b/front_end/ui/legacy/components/perf_ui/ChartViewport.ts
index 2ec7c22..8d8f9ff 100644
--- a/front_end/ui/legacy/components/perf_ui/ChartViewport.ts
+++ b/front_end/ui/legacy/components/perf_ui/ChartViewport.ts
@@ -53,7 +53,7 @@
 
   constructor(delegate: ChartViewportDelegate) {
     super();
-    this.registerRequiredCSS('ui/legacy/components/perf_ui/chartViewport.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/perf_ui/chartViewport.css');
 
     this._delegate = delegate;
 
diff --git a/front_end/ui/legacy/components/perf_ui/FilmStripView.ts b/front_end/ui/legacy/components/perf_ui/FilmStripView.ts
index e07db8b..8dd8513 100644
--- a/front_end/ui/legacy/components/perf_ui/FilmStripView.ts
+++ b/front_end/ui/legacy/components/perf_ui/FilmStripView.ts
@@ -44,7 +44,7 @@
 
   constructor() {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/perf_ui/filmStripView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/perf_ui/filmStripView.css');
     this.contentElement.classList.add('film-strip-view');
     this._statusLabel = this.contentElement.createChild('div', 'label');
     this.reset();
diff --git a/front_end/ui/legacy/components/perf_ui/FlameChart.ts b/front_end/ui/legacy/components/perf_ui/FlameChart.ts
index 6e124e5..7b95742 100644
--- a/front_end/ui/legacy/components/perf_ui/FlameChart.ts
+++ b/front_end/ui/legacy/components/perf_ui/FlameChart.ts
@@ -158,7 +158,7 @@
       dataProvider: FlameChartDataProvider, flameChartDelegate: FlameChartDelegate,
       groupExpansionSetting?: Common.Settings.Setting<GroupExpansionState>) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/perf_ui/flameChart.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/perf_ui/flameChart.css');
     this.contentElement.classList.add('flame-chart-main-pane');
     this._groupExpansionSetting = groupExpansionSetting;
     this._groupExpansionState = groupExpansionSetting && groupExpansionSetting.get() || {};
diff --git a/front_end/ui/legacy/components/perf_ui/OverviewGrid.ts b/front_end/ui/legacy/components/perf_ui/OverviewGrid.ts
index 7ebf442..19b24e2 100644
--- a/front_end/ui/legacy/components/perf_ui/OverviewGrid.ts
+++ b/front_end/ui/legacy/components/perf_ui/OverviewGrid.ts
@@ -163,8 +163,7 @@
 
     this._parentElement.addEventListener('wheel', this._onMouseWheel.bind(this), true);
     this._parentElement.addEventListener('dblclick', this._resizeWindowMaximum.bind(this), true);
-    UI.Utils.appendStyle(
-        this._parentElement, 'ui/legacy/components/perf_ui/overviewGrid.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(this._parentElement, 'ui/legacy/components/perf_ui/overviewGrid.css');
 
     this._leftResizeElement = parentElement.createChild('div', 'overview-grid-window-resizer') as HTMLElement;
     UI.UIUtils.installDragHandle(
diff --git a/front_end/ui/legacy/components/perf_ui/TimelineGrid.ts b/front_end/ui/legacy/components/perf_ui/TimelineGrid.ts
index 2be30e9..bf41cee 100644
--- a/front_end/ui/legacy/components/perf_ui/TimelineGrid.ts
+++ b/front_end/ui/legacy/components/perf_ui/TimelineGrid.ts
@@ -49,7 +49,7 @@
 
   constructor() {
     this.element = document.createElement('div');
-    UI.Utils.appendStyle(this.element, 'ui/legacy/components/perf_ui/timelineGrid.css', {enableLegacyPatching: false});
+    UI.Utils.appendStyle(this.element, 'ui/legacy/components/perf_ui/timelineGrid.css');
 
     this._dividersElement = this.element.createChild('div', 'resources-dividers');
 
diff --git a/front_end/ui/legacy/components/perf_ui/TimelineOverviewPane.ts b/front_end/ui/legacy/components/perf_ui/TimelineOverviewPane.ts
index 903e437..09bc77f 100644
--- a/front_end/ui/legacy/components/perf_ui/TimelineOverviewPane.ts
+++ b/front_end/ui/legacy/components/perf_ui/TimelineOverviewPane.ts
@@ -420,7 +420,6 @@
     this._element = UI.Utils
                         .createShadowRootWithCoreStyles(this._glassPane.contentElement, {
                           cssFile: 'ui/legacy/components/perf_ui/timelineOverviewInfo.css',
-                          enableLegacyPatching: false,
                           delegatesFocus: undefined,
                         })
                         .createChild('div', 'overview-info');
diff --git a/front_end/ui/legacy/components/quick_open/FilteredListWidget.ts b/front_end/ui/legacy/components/quick_open/FilteredListWidget.ts
index af826c9..be5c2b6 100644
--- a/front_end/ui/legacy/components/quick_open/FilteredListWidget.ts
+++ b/front_end/ui/legacy/components/quick_open/FilteredListWidget.ts
@@ -62,7 +62,7 @@
     const listener = (this._onKeyDown.bind(this) as (arg0: Event) => void);
     this.contentElement.addEventListener('keydown', listener, true);
     UI.ARIAUtils.markAsCombobox(this.contentElement);
-    this.registerRequiredCSS('ui/legacy/components/quick_open/filteredListWidget.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/quick_open/filteredListWidget.css');
 
     this._promptElement = this.contentElement.createChild('div', 'filtered-list-widget-input');
     UI.ARIAUtils.setAccessibleName(this._promptElement, i18nString(UIStrings.quickOpenPrompt));
diff --git a/front_end/ui/legacy/components/source_frame/FontView.ts b/front_end/ui/legacy/components/source_frame/FontView.ts
index 2d61685..ede5d25 100644
--- a/front_end/ui/legacy/components/source_frame/FontView.ts
+++ b/front_end/ui/legacy/components/source_frame/FontView.ts
@@ -61,7 +61,7 @@
   _inResize!: boolean|null;
   constructor(mimeType: string, contentProvider: TextUtils.ContentProvider.ContentProvider) {
     super(i18nString(UIStrings.font));
-    this.registerRequiredCSS('ui/legacy/components/source_frame/fontView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/source_frame/fontView.css');
     this.element.classList.add('font-view');
     this._url = contentProvider.contentURL();
     UI.ARIAUtils.setAccessibleName(this.element, i18nString(UIStrings.previewOfFontFromS, {PH1: this._url}));
diff --git a/front_end/ui/legacy/components/source_frame/ImageView.ts b/front_end/ui/legacy/components/source_frame/ImageView.ts
index 0a0d5ad..e22e3bd 100644
--- a/front_end/ui/legacy/components/source_frame/ImageView.ts
+++ b/front_end/ui/legacy/components/source_frame/ImageView.ts
@@ -98,7 +98,7 @@
   _cachedContent?: string|null;
   constructor(mimeType: string, contentProvider: TextUtils.ContentProvider.ContentProvider) {
     super(i18nString(UIStrings.image));
-    this.registerRequiredCSS('ui/legacy/components/source_frame/imageView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/source_frame/imageView.css');
     this.element.tabIndex = -1;
     this.element.classList.add('image-view');
     this._url = contentProvider.contentURL();
diff --git a/front_end/ui/legacy/components/source_frame/JSONView.ts b/front_end/ui/legacy/components/source_frame/JSONView.ts
index 6448232..cb2303f 100644
--- a/front_end/ui/legacy/components/source_frame/JSONView.ts
+++ b/front_end/ui/legacy/components/source_frame/JSONView.ts
@@ -56,7 +56,7 @@
   constructor(parsedJSON: ParsedJSON, startCollapsed?: boolean) {
     super();
     this._initialized = false;
-    this.registerRequiredCSS('ui/legacy/components/source_frame/jsonView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/source_frame/jsonView.css');
     this._parsedJSON = parsedJSON;
     this._startCollapsed = Boolean(startCollapsed);
     this.element.classList.add('json-view');
diff --git a/front_end/ui/legacy/components/source_frame/ResourceSourceFrame.ts b/front_end/ui/legacy/components/source_frame/ResourceSourceFrame.ts
index 246ab42..816a8f0 100644
--- a/front_end/ui/legacy/components/source_frame/ResourceSourceFrame.ts
+++ b/front_end/ui/legacy/components/source_frame/ResourceSourceFrame.ts
@@ -80,8 +80,7 @@
 
   constructor(resource: TextUtils.ContentProvider.ContentProvider, highlighterType: string, autoPrettyPrint?: boolean) {
     super(true);
-    this.registerRequiredCSS(
-        'ui/legacy/components/source_frame/resourceSourceFrame.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/source_frame/resourceSourceFrame.css');
     const sourceFrame = new ResourceSourceFrame(resource, autoPrettyPrint);
     this._sourceFrame = sourceFrame;
     sourceFrame.setHighlighterType(highlighterType);
diff --git a/front_end/ui/legacy/components/source_frame/XMLView.ts b/front_end/ui/legacy/components/source_frame/XMLView.ts
index 17065ff..a9defcd 100644
--- a/front_end/ui/legacy/components/source_frame/XMLView.ts
+++ b/front_end/ui/legacy/components/source_frame/XMLView.ts
@@ -27,11 +27,10 @@
 
   constructor(parsedXML: Document) {
     super(true);
-    this.registerRequiredCSS('ui/legacy/components/source_frame/xmlView.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('ui/legacy/components/source_frame/xmlView.css');
     this.contentElement.classList.add('shadow-xml-view', 'source-code');
     this._treeOutline = new UI.TreeOutline.TreeOutlineInShadow();
-    this._treeOutline.registerRequiredCSS(
-        'ui/legacy/components/source_frame/xmlTree.css', {enableLegacyPatching: false});
+    this._treeOutline.registerRequiredCSS('ui/legacy/components/source_frame/xmlTree.css');
     this.contentElement.appendChild(this._treeOutline.element);
     this._currentSearchFocusIndex = 0;
     this._currentSearchTreeElements = [];
diff --git a/front_end/ui/legacy/components/text_editor/CodeMirrorTextEditor.ts b/front_end/ui/legacy/components/text_editor/CodeMirrorTextEditor.ts
index eb24554..49ba07c 100644
--- a/front_end/ui/legacy/components/text_editor/CodeMirrorTextEditor.ts
+++ b/front_end/ui/legacy/components/text_editor/CodeMirrorTextEditor.ts
@@ -92,8 +92,8 @@
     super();
     this._options = options;
 
-    this.registerRequiredCSS('third_party/codemirror/codemirror.css', {enableLegacyPatching: false});
-    this.registerRequiredCSS('ui/legacy/components/text_editor/cmdevtools.css', {enableLegacyPatching: false});
+    this.registerRequiredCSS('third_party/codemirror/codemirror.css');
+    this.registerRequiredCSS('ui/legacy/components/text_editor/cmdevtools.css');
 
     const {indentWithTabs, indentUnit} = CodeMirrorTextEditor._getIndentation(
         Common.Settings.Settings.instance().moduleSetting('textEditorIndent').get());
diff --git a/front_end/ui/legacy/components/text_editor/TextEditorAutocompleteController.ts b/front_end/ui/legacy/components/text_editor/TextEditorAutocompleteController.ts
index 88d323a..fbc24e6 100644
--- a/front_end/ui/legacy/components/text_editor/TextEditorAutocompleteController.ts
+++ b/front_end/ui/legacy/components/text_editor/TextEditorAutocompleteController.ts
@@ -61,7 +61,6 @@
     this._tooltipElement.classList.add('autocomplete-tooltip');
     const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(this._tooltipGlassPane.contentElement, {
       cssFile: 'ui/legacy/components/text_editor/autocompleteTooltip.css',
-      enableLegacyPatching: false,
       delegatesFocus: undefined,
     });
     shadowRoot.appendChild(this._tooltipElement);
diff --git a/front_end/ui/legacy/components/utils/ImagePreview.ts b/front_end/ui/legacy/components/utils/ImagePreview.ts
index 48392fe..5913ee3 100644
--- a/front_end/ui/legacy/components/utils/ImagePreview.ts
+++ b/front_end/ui/legacy/components/utils/ImagePreview.ts
@@ -103,7 +103,7 @@
 
     function buildContent(): void {
       const container = document.createElement('table');
-      UI.Utils.appendStyle(container, 'ui/legacy/components/utils/imagePreview.css', {enableLegacyPatching: false});
+      UI.Utils.appendStyle(container, 'ui/legacy/components/utils/imagePreview.css');
       container.className = 'image-preview-container';
 
       const imageRow = (container.createChild('tr').createChild('td', 'image-container') as HTMLTableDataCellElement);
diff --git a/front_end/ui/legacy/components/utils/JSPresentationUtils.ts b/front_end/ui/legacy/components/utils/JSPresentationUtils.ts
index 01335b4..f91944a 100644
--- a/front_end/ui/legacy/components/utils/JSPresentationUtils.ts
+++ b/front_end/ui/legacy/components/utils/JSPresentationUtils.ts
@@ -202,8 +202,7 @@
   element.classList.add('monospace');
   element.style.display = 'inline-block';
   const shadowRoot = UI.Utils.createShadowRootWithCoreStyles(
-      element,
-      {cssFile: 'ui/legacy/components/utils/jsUtils.css', enableLegacyPatching: false, delegatesFocus: undefined});
+      element, {cssFile: 'ui/legacy/components/utils/jsUtils.css', delegatesFocus: undefined});
   const contentElement = shadowRoot.createChild('table', 'stack-preview-container');
   if (!stackTrace) {
     return {element, links: []};
diff --git a/front_end/ui/legacy/theme_support/theme_support_impl.ts b/front_end/ui/legacy/theme_support/theme_support_impl.ts
index 4df9dd6..3b8e846 100644
--- a/front_end/ui/legacy/theme_support/theme_support_impl.ts
+++ b/front_end/ui/legacy/theme_support/theme_support_impl.ts
@@ -114,9 +114,9 @@
 
   injectHighlightStyleSheets(element: Element|ShadowRoot): void {
     this._injectingStyleSheet = true;
-    this._appendStyle(element, 'ui/legacy/inspectorSyntaxHighlight.css', {enableLegacyPatching: false});
+    this._appendStyle(element, 'ui/legacy/inspectorSyntaxHighlight.css');
     if (this._themeName === 'dark') {
-      this._appendStyle(element, 'ui/legacy/inspectorSyntaxHighlightDark.css', {enableLegacyPatching: false});
+      this._appendStyle(element, 'ui/legacy/inspectorSyntaxHighlightDark.css');
     }
     this._injectingStyleSheet = false;
   }
@@ -125,29 +125,14 @@
    * Note: this is a duplicate of the function in ui/utils. It exists here
    * so there is no circular dependency between ui/utils and theme_support.
    */
-  _appendStyle(node: Node, cssFile: string, options: {
-    enableLegacyPatching: false,
-  } = {enableLegacyPatching: false}): void {
+  _appendStyle(node: Node, cssFile: string): void {
     const content = Root.Runtime.cachedResources.get(cssFile) || '';
     if (!content) {
       console.error(cssFile + ' not preloaded. Check module.json');
     }
-    let styleElement = document.createElement('style');
+    const styleElement = document.createElement('style');
     styleElement.textContent = content;
     node.appendChild(styleElement);
-
-    /**
-     * We are incrementally removing patching support in favour of CSS variables for supporting dark mode.
-     * See https://docs.google.com/document/d/1QrSSRsJRzaQBY3zz73ZL84bTcFUV60yMtE5cuu6ED14 for details.
-     */
-    if (options.enableLegacyPatching) {
-      const themeStyleSheet = ThemeSupport.instance().themeStyleSheet(cssFile, content);
-      if (themeStyleSheet) {
-        styleElement = document.createElement('style');
-        styleElement.textContent = themeStyleSheet + '\n' + Root.Runtime.Runtime.resolveSourceURL(cssFile + '.theme');
-        node.appendChild(styleElement);
-      }
-    }
   }
 
   injectCustomStyleSheets(element: Element|ShadowRoot): void {
diff --git a/front_end/ui/legacy/utils/append-style.ts b/front_end/ui/legacy/utils/append-style.ts
index b600249..15f1ae7 100644
--- a/front_end/ui/legacy/utils/append-style.ts
+++ b/front_end/ui/legacy/utils/append-style.ts
@@ -3,29 +3,13 @@
 // found in the LICENSE file.
 
 import * as Root from '../../../core/root/root.js';
-import * as ThemeSupport from '../theme_support/theme_support.js';
 
-export function appendStyle(node: Node, cssFile: string, options: {enableLegacyPatching: false} = {
-  enableLegacyPatching: false,
-}): void {
+export function appendStyle(node: Node, cssFile: string): void {
   const content = Root.Runtime.cachedResources.get(cssFile) || '';
   if (!content) {
     console.error(cssFile + ' not preloaded. Check module.json');
   }
-  let styleElement = document.createElement('style');
+  const styleElement = document.createElement('style');
   styleElement.textContent = content;
   node.appendChild(styleElement);
-
-  /**
-   * We are incrementally removing patching support in favour of CSS variables for supporting dark mode.
-   * See https://docs.google.com/document/d/1QrSSRsJRzaQBY3zz73ZL84bTcFUV60yMtE5cuu6ED14 for details.
-   */
-  if (options.enableLegacyPatching) {
-    const themeStyleSheet = ThemeSupport.ThemeSupport.instance().themeStyleSheet(cssFile, content);
-    if (themeStyleSheet) {
-      styleElement = document.createElement('style');
-      styleElement.textContent = themeStyleSheet + '\n' + Root.Runtime.Runtime.resolveSourceURL(cssFile + '.theme');
-      node.appendChild(styleElement);
-    }
-  }
 }
diff --git a/front_end/ui/legacy/utils/create-shadow-root-with-core-styles.ts b/front_end/ui/legacy/utils/create-shadow-root-with-core-styles.ts
index def0eaf..3fdc71a 100644
--- a/front_end/ui/legacy/utils/create-shadow-root-with-core-styles.ts
+++ b/front_end/ui/legacy/utils/create-shadow-root-with-core-styles.ts
@@ -9,24 +9,21 @@
 interface Options {
   cssFile?: string;
   delegatesFocus?: boolean;
-  enableLegacyPatching: false;
 }
 
 export function createShadowRootWithCoreStyles(element: Element, options: Options = {
   delegatesFocus: undefined,
   cssFile: undefined,
-  enableLegacyPatching: false,
 }): ShadowRoot {
   const {
     cssFile,
     delegatesFocus,
-    enableLegacyPatching,
   } = options;
 
   const shadowRoot = element.attachShadow({mode: 'open', delegatesFocus});
   injectCoreStyles(shadowRoot);
   if (cssFile) {
-    appendStyle(shadowRoot, cssFile, {enableLegacyPatching});
+    appendStyle(shadowRoot, cssFile);
   }
   shadowRoot.addEventListener('focus', focusChanged, true);
   return shadowRoot;
diff --git a/front_end/ui/legacy/utils/inject-core-styles.ts b/front_end/ui/legacy/utils/inject-core-styles.ts
index 5b666f2..6d85c50 100644
--- a/front_end/ui/legacy/utils/inject-core-styles.ts
+++ b/front_end/ui/legacy/utils/inject-core-styles.ts
@@ -7,10 +7,10 @@
 
 export function injectCoreStyles(root: Element|ShadowRoot): void {
   // TODO: Migrate inspectorCommpon.css last https://crbug.com/1222666
-  appendStyle(root, 'ui/legacy/inspectorCommon.css', {enableLegacyPatching: false});
-  appendStyle(root, 'ui/legacy/inspectorScrollbars.css', {enableLegacyPatching: false});
-  appendStyle(root, 'ui/legacy/textButton.css', {enableLegacyPatching: false});
-  appendStyle(root, 'ui/legacy/themeColors.css', {enableLegacyPatching: false});
+  appendStyle(root, 'ui/legacy/inspectorCommon.css');
+  appendStyle(root, 'ui/legacy/inspectorScrollbars.css');
+  appendStyle(root, 'ui/legacy/textButton.css');
+  appendStyle(root, 'ui/legacy/themeColors.css');
 
   ThemeSupport.ThemeSupport.instance().injectHighlightStyleSheets(root);
   ThemeSupport.ThemeSupport.instance().injectCustomStyleSheets(root);