MD Bookmarks: Batch updates to the UI when processing deletes and moves

chrome/browser/resources/md_bookmarks/dnd_manager.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('bookmarks', function() {
   /**
    * @param {BookmarkElement} element
    * @return {boolean}
    */
   function isBookmarkItem(element) {
@@ skipping 318 matching lines @@
 
     /**
      * @private
      * @param {!Event} e
      */
     onDrop_: function(e) {
       if (this.dropDestination_) {
         e.preventDefault();
 
         var dropInfo = this.calculateDropInfo_(this.dropDestination_);
-        if (dropInfo.index != -1)
-          chrome.bookmarkManagerPrivate.drop(dropInfo.parentId, dropInfo.index);
-        else
-          chrome.bookmarkManagerPrivate.drop(dropInfo.parentId);
+        var index = dropInfo.index != -1 ? dropInfo.index : undefined;
+        var store = bookmarks.Store.getInstance();
+        store.beginBatchUpdate();
+        chrome.bookmarkManagerPrivate.drop(

[calamity, 2017/06/22 05:48:27]

This works within the BMM, but moving a folder in the bookmarks bar will still
cause the burst of move events. Can we start the batch update in onDragEnter and
end it in onDrop instead?

[tsergeant, 2017/06/23 00:20:20]

Hmmm, good idea, but I'm not sure that this is possible.

When I drag BMM -> bookmarks bar, the chrome.bookmarksManagerPrivate.onDrop
listener never fires. Instead, we just get onDragLeave and then the
onBookmarkMoved calls.

Even dragging BMM->BMM doesn't work well, since the
bookmarksManagerPrivate.onDrop listener fires before the onBookmarkMoved calls.

[calamity, 2017/06/26 03:17:24]

Hmm. How about just batching in api_listener.js? Having a 100ms debouncer for
all events fired probably isn't unreasonable and would handle all EventStorms.

[tsergeant, 2017/06/27 07:35:53]

Done. As discussed, I setTimeout seems to work reliably on my machine. We'll
probably need to double check that it works okay on other machines as well after
this lands.

+            dropInfo.parentId, index, function() {
+              store.endBatchUpdate();
+            });
       }
 
       this.dropDestination_ = null;
       this.dropIndicator_.finish();
     },
 
     /**
      * @param {DropDestination} dropDestination
      * @return {{parentId: string, index: number}}
      */
@@ skipping 292 matching lines @@
       this.dropIndicator_.setTimeout = this.setTimeout_;
     }
   };
 
   return {
     DNDManager: DNDManager,
     DragInfo: DragInfo,
     DropIndicator: DropIndicator,
   };
 });