[MD Bookmarks] Modify search to retain the previously selected folder.

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',
 
   properties: {
     /** @type {BookmarkTreeNode} */
     item: Object,
@@ skipping 16 matching lines @@
   /**
    * @private
    * @return {string}
    */
   getArrowIcon_: function() {
     return this.item.isOpen ? 'cr:arrow-drop-up' : 'cr:arrow-drop-down';
   },
 
   /** @private */
   selectFolder_: function() {
+    this.fire('search-term-changed', '');
     this.fire('selected-folder-changed', this.item.id);
   },
 
   /**
    * Occurs when the drop down arrow is tapped.
    * @private
    */
   toggleFolder_: function() {
     this.fire('folder-open-changed', {
       id: this.item.id,
       open: !this.item.isOpen,
     });
   },
 
   /**
    * @private
    * @return {boolean}
    */
   hasChildFolder_: function() {
     for (var i = 0; i < this.item.children.length; i++) {
       if (!this.item.children[i].url)
         return true;
     }
     return false;
   },
 });