MD Settings: Add mechanism to restore focus after subpage exiting.

chrome/browser/resources/settings/search_page/search_page.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'settings-search-page' is the settings page containing search settings.
  */
 Polymer({
   is: 'settings-search-page',
@@ skipping 21 matching lines @@
      * This is a local PrefObject used to reflect the enabled state of hotword
      * search. It is not tied directly to a pref. (There are two prefs
      * associated with  state and they do not map directly to whether or not
      * hotword search is actually enabled).
      * @private {!chrome.settingsPrivate.PrefObject|undefined}
      */
     hotwordSearchEnablePref_: Object,
 
     /** @private */
     googleNowAvailable_: Boolean,
+
+    /** @type {?Map<string, string>} */
+    focusConfig_: Object,
   },
 
   /** @private {?settings.SearchEnginesBrowserProxy} */
   browserProxy_: null,
 
   /** @override */
   created: function() {
     this.browserProxy_ = settings.SearchEnginesBrowserProxyImpl.getInstance();
   },
 
@@ skipping 11 matching lines @@
     cr.addWebUIListener(
         'hotword-info-update', this.hotwordInfoUpdate_.bind(this));
 
     // Google Now cards in the launcher
     cr.addWebUIListener(
         'google-now-availability-changed',
         this.googleNowAvailabilityUpdate_.bind(this));
     this.browserProxy_.getGoogleNowAvailability().then(function(available) {
         this.googleNowAvailabilityUpdate_(available);
     }.bind(this));
+
+    this.focusConfig_ = new Map();
+    this.focusConfig_.set(
+        settings.Route.SEARCH_ENGINES.path, '#subpage-trigger .subpage-arrow');
   },
 
   /** @private */
   onChange_: function() {
     var select = /** @type {!HTMLSelectElement} */ (this.$$('select'));
     var searchEngine = this.searchEngines_[select.selectedIndex];
     this.browserProxy_.setDefaultSearchEngine(searchEngine.modelIndex);
   },
 
   /** @private */
@@ skipping 82 matching lines @@
   },
 
   /**
    * @param {Event} event
    * @private
    */
   doNothing_: function(event) {
     event.stopPropagation();
   }
 });