[elements] Show horizontal scroll bar for Properties tab.

Screenshot: https://imgur.com/VeVWv8G.png
Fixed: chromium:1283364
Change-Id: I20e88f10e1cd7b207c84b2c0c7c4b72385ceb81b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/5126311
Auto-Submit: Benedikt Meurer <[email protected]>
Reviewed-by: Philip Pfaffe <[email protected]>
Commit-Queue: Philip Pfaffe <[email protected]>
diff --git a/front_end/panels/sources/WatchExpressionsSidebarPane.ts b/front_end/panels/sources/WatchExpressionsSidebarPane.ts
index c6659e4..e37c51a 100644
--- a/front_end/panels/sources/WatchExpressionsSidebarPane.ts
+++ b/front_end/panels/sources/WatchExpressionsSidebarPane.ts
@@ -123,6 +123,7 @@
     this.contentElement.setAttribute('jslog', `${VisualLogging.pane().context('debugger-watch')}`);
     this.contentElement.addEventListener('contextmenu', this.contextMenu.bind(this), false);
     this.treeOutline = new ObjectUI.ObjectPropertiesSection.ObjectPropertiesSectionsTreeOutline();
+    this.treeOutline.hideOverflow();
 
     this.treeOutline.setShowSelectionOnKeyboardFocus(/* show */ true);
     this.expandController =