[MD Bookmarks] Convert bookmark list to iron-list.

chrome/browser/resources/md_bookmarks/item.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-item',
 
   behaviors: [
     bookmarks.StoreClient,
   ],
 
   properties: {
     itemId: {
       type: String,
       observer: 'onItemIdChanged_',
     },
 
+    ironListTabIndex: String,
+
     /** @private {BookmarkNode} */
     item_: {
       type: Object,
       observer: 'onItemChanged_',
     },
 
     /** @private */
     isSelectedItem_: {
       type: Boolean,
       reflectToAttribute: true,
     },
 
     /** @private */
+    mouseFocus_: {
+      type: Boolean,
+      reflectToAttribute: true,
+    },
+
+    /** @private */
     isFolder_: Boolean,
   },
 
   observers: [
     'updateFavicon_(item_.url)',
   ],
 
   listeners: {
+    'mousedown': 'onMousedown_',
+    'blur': 'onBlur_',
     'click': 'onClick_',
     'dblclick': 'onDblClick_',
     'contextmenu': 'onContextMenu_',
   },
 
   /** @override */
   attached: function() {
     this.watch('item_', function(store) {
       return store.nodes[this.itemId];
     }.bind(this));
@@ skipping 53 matching lines @@
     assert(this.getState().nodes[this.itemId]);
     this.updateFromStore();
   },
 
   /** @private */
   onItemChanged_: function() {
     this.isFolder_ = !this.item_.url;
   },
 
   /**
+   * @private
+   */
+  onMousedown_: function() {
+    this.mouseFocus_ = true;

[tsergeant, 2017/05/15 01:14:27]

I think this is going to be buggy. For example, I can mousedown on an item, drag
my mouse away from it and then mouseup on a different item. This will apply
mouseFocus_ without ever focusing the item, and if I then keyboard focus the
item, no outline will show up.

You could check the focus-ring polyfill to see the approach it takes (kind of
the opposite).

[calamity, 2017/05/16 02:54:15]

Added the focus handler to the button as discussed.

+  },
+
+  /**
+   * @private
+   */
+  onBlur_: function() {
+    this.mouseFocus_ = false;
+  },
+
+  /**
    * @param {Event} e
    * @private
    */
   onClick_: function(e) {
     this.dispatch(bookmarks.actions.selectItem(
         this.itemId, e.ctrlKey, e.shiftKey, this.getState()));
     e.stopPropagation();
   },
 
   /**
@@ skipping 10 matching lines @@
   },
 
   /**
    * @param {string} url
    * @private
    */
   updateFavicon_: function(url) {
     this.$.icon.style.backgroundImage = cr.icon.getFavicon(url);
   },
 });