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

chrome/browser/resources/md_bookmarks/router.js

 // Copyright 2017 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({
   /**
    * This element is a one way bound interface that routes the page URL to
    * the searchTerm and selectedId. Clients must initialize themselves by
    * reading the router's fields after attach.
    */
@@ skipping 17 matching lines @@
   },
 
   observers: [
     'onQueryChanged_(queryParams_.*)',
   ],
 
   /** @private */
   onQueryChanged_: function() {
     this.searchTerm = this.queryParams_.q || '';
     this.selectedId = this.queryParams_.id;
-
-    if (this.searchTerm)
-      this.fire('search-term-changed', this.searchTerm);
-    else
-      this.fire('selected-folder-changed', this.selectedId);
+    this.fire('selected-folder-changed', {id: this.selectedId});
+    this.fire('search-term-changed', this.searchTerm);
   },
 
   /** @private */
   onSelectedIdChanged_: function() {
     this.set('queryParams_.id', this.selectedId || null);
   },
 
   /** @private */
   onSearchTermChanged_: function() {
     this.set('queryParams_.q', this.searchTerm || null);
   },
 });