DevTools: filter out "snippets" filesystem from Workspace Settings

R=dgozman

Change-Id: Ieef8860b2ee7e65f013e4a01144b7812f3cf5af9
Reviewed-on: https://chromium-review.googlesource.com/c/1345534
Reviewed-by: Dmitry Gozman <[email protected]>
Commit-Queue: Andrey Lushnikov <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#609933}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b96a2016f5c8e713a6976d2c52b23ba214075524
diff --git a/front_end/persistence/WorkspaceSettingsTab.js b/front_end/persistence/WorkspaceSettingsTab.js
index 5930811..7f9c03d 100644
--- a/front_end/persistence/WorkspaceSettingsTab.js
+++ b/front_end/persistence/WorkspaceSettingsTab.js
@@ -78,6 +78,9 @@
    * @param {!Persistence.PlatformFileSystem} fileSystem
    */
   _addItem(fileSystem) {
+    // Support managing only instances of IsolatedFileSystem.
+    if (!(fileSystem instanceof Persistence.IsolatedFileSystem))
+      return;
     const networkPersistenceProject = Persistence.networkPersistenceManager.project();
     if (networkPersistenceProject &&
         Persistence.isolatedFileSystemManager.fileSystem(networkPersistenceProject.fileSystemPath()) === fileSystem)