[MD Bookmarks] Add keyboard navigation to 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: {
     /** @private */
     searchTerm_: {
       type: String,
       observer: 'searchTermChanged_',
     },
 
     /** @type {ClosedFolderState} */
     closedFoldersState_: {
       type: Object,
       observer: 'closedFoldersStateChanged_',
     },
 
     /** @private */
     sidebarWidth_: String,
   },
 
+  listeners: {
+    'folder-node-focus-changed': 'onFolderNodeFocusChanged_',
+  },
+
   /** @private{?function(!Event)} */
   boundUpdateSidebarWidth_: null,
 
   /** @private {bookmarks.DNDManager} */
   dndManager_: null,
 
+  /** @private {BookmarksFolderNode} */
+  focusedFolderNode_: null,
+
   /** @override */
   attached: function() {
     this.watch('searchTerm_', function(store) {
       return store.search.term;
     });
 
     this.watch('closedFoldersState_', function(store) {
       return store.closedFolders;
     });
 
@@ skipping 47 matching lines @@
     splitter.addEventListener('resize', function(e) {
       window.localStorage[LOCAL_STORAGE_TREE_WIDTH_KEY] =
           splitterTarget.style.width;
       this.updateSidebarWidth_();
     }.bind(this));
 
     splitter.addEventListener('dragmove', this.boundUpdateSidebarWidth_);
     window.addEventListener('resize', this.boundUpdateSidebarWidth_);
   },
 
+  onFolderNodeFocusChanged_: function(e) {
+    if (this.focusedFolderNode_)
+      this.focusedFolderNode_.focusable = false;
+
+    this.focusedFolderNode_ = e.detail;
+    this.focusedFolderNode_ = true;

[tsergeant, 2017/04/19 01:42:16]

What's going on here? My guess is this was supposed to be

this.focusedFolderNode_.focusable = true;

?

[calamity, 2017/04/19 04:51:02]

Done.

+  },
+
   /** @private */
   updateSidebarWidth_: function() {
     this.sidebarWidth_ =
         /** @type {string} */ (getComputedStyle(this.$.sidebar).width);
   },
 
   /** @private */
   searchTermChanged_: function() {
     if (!this.searchTerm_)
       return;
 
     chrome.bookmarks.search(this.searchTerm_, function(results) {
       var ids = results.map(function(node) {
         return node.id;
       });
       this.dispatch(bookmarks.actions.setSearchResults(ids));
     }.bind(this));
   },
 
   /** @private */
   closedFoldersStateChanged_: function() {
     window.localStorage[LOCAL_STORAGE_CLOSED_FOLDERS_KEY] =
         JSON.stringify(Array.from(this.closedFoldersState_));
   },
 });