Settings Router Refactor: Remove route.page legacy property.

chrome/browser/resources/settings/settings_menu/settings_menu.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-menu' shows a menu with a hardcoded set of pages and subpages.
  */
 Polymer({
   is: 'settings-menu',
@@ skipping 22 matching lines @@
     }.bind(this));
 
     this.$.advancedPage.addEventListener('paper-submenu-open', function() {
       this.fire('toggle-advanced-page', true);
     }.bind(this));
 
     this.$.advancedPage.addEventListener('paper-submenu-close', function() {
       this.fire('toggle-advanced-page', false);
     }.bind(this));
 
-    this.fire('toggle-advanced-page', this.currentRoute.page == 'advanced');
+    this.fire('toggle-advanced-page',
+              this.currentRoute.inSubtreeOf(settings.Route.ADVANCED));
   },
 
   /**
    * @param {!settings.Route} newRoute
    * @private
    */
   currentRouteChanged_: function(newRoute) {
     // Sync URL changes to the side nav menu.
     this.$.advancedMenu.selected = this.currentRoute.path;
     this.$.basicMenu.selected = this.currentRoute.path;
@@ skipping 27 matching lines @@
 
   /**
    * @param {boolean} opened Whether the menu is expanded.
    * @return {string} Which icon to use.
    * @private
    * */
   arrowState_: function(opened) {
     return opened ? 'settings:arrow-drop-up' : 'cr:arrow-drop-down';
   },
 });