[MD Bookmarks] Flatten sidebar.

chrome/browser/resources/md_bookmarks/app.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-app',
 
   behaviors: [
     bookmarks.StoreClient,
   ],
 
   properties: {
     searchTerm: {
       type: String,
       observer: 'searchTermChanged_',
     },
   },
 
   /** @override */
   attached: function() {
     this.observe('searchTerm', function(store) {
       return store.search.term;
     });
 
     chrome.bookmarks.getTree(function(results) {
-      var nodeList = bookmarks.util.normalizeNodes(results[0]);
+      var rootNode = results[0];
+      var nodeList = bookmarks.util.normalizeNodes(rootNode);
       var initialState = bookmarks.util.createEmptyState();
       initialState.nodes = nodeList;
-      initialState.selectedFolder = nodeList['0'].children[0];
+      initialState.selectedFolder = nodeList[rootNode.id].children[0];
+      initialState.sidebar =
+          bookmarks.util.initializeSidebar(rootNode.id, nodeList);
 
       // TODO(tsergeant): The below ends up slightly duplicating logic from
       // elsewhere. Consider trying to use actions/reducers to simplify this.
       var router = this.$.router;
       if (router.searchTerm) {
         initialState.selectedFolder = null;
         initialState.search.term = router.searchTerm;
         initialState.search.inProgress = true;
       } else if (router.selectedId) {
         initialState.selectedFolder = router.selectedId;
       }
 
       bookmarks.Store.getInstance().init(initialState);
       bookmarks.ApiListener.init();
     }.bind(this));
   },
 
   searchTermChanged_: function() {
     if (this.searchTerm) {
       chrome.bookmarks.search(this.searchTerm, function(results) {
         this.dispatch(bookmarks.actions.setSearchResults(results));
       }.bind(this));
     }
   },
 });