[MD Bookmarks] Persist collapsed folders between page loads.

chrome/browser/resources/md_bookmarks/folder_node.js

 // Copyright 2016 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.
 
 Polymer({
   is: 'bookmarks-folder-node',
 
   behaviors: [
     bookmarks.StoreClient,
   ],
@@ skipping 61 matching lines @@
   },
 
   /**
    * Occurs when the drop down arrow is tapped.
    * @private
    * @param {!Event} e
    */
   toggleFolder_: function(e) {
     this.dispatch(
         bookmarks.actions.changeFolderOpen(this.item_.id, this.isClosed_));
+    window.localStorage[LOCAL_STORAGE_CLOSED_FOLDERS_KEY] =

[tsergeant, 2017/03/29 04:43:24]

I'm a bit torn about where this should live. On one hand, maybe it should live
in app.js, alongside the code which loads the state from localstorage. On the
other hand, it does kind of make sense to have it here where it changes.

Did you think about putting it in app? Any particular reason why you went for
here?

[calamity, 2017/03/30 03:16:04]

Yeah, basically because this is where it changes. I think you're right actually.
This won't pick up more subtle things like openAncestorFolders etc.

+        JSON.stringify(this.getState().closedFolders);
     e.stopPropagation();
   },
 
   /**
    * @private
    * @param {string} itemId
    * @param {string} selectedFolder
    * @return {boolean}
    */
   computeIsSelected_: function(itemId, selectedFolder) {
@@ skipping 31 matching lines @@
   },
 
   /**
    * @private
    * @return {boolean}
    */
   isRootFolder_: function() {
     return this.depth == 0;
   },
 });