MD Settings: rework how advanced UI shows

chrome/browser/resources/settings/settings_ui/settings_ui.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-ui' implements the UI for the Settings page.
  *
  * Example:
  *
@@ skipping 14 matching lines @@
      */
     prefs: Object,
 
     /** @type {?settings.DirectionDelegate} */
     directionDelegate: {
       observer: 'directionDelegateChanged_',
       type: Object,
       value: new settings.DirectionDelegateImpl(),
     },
 
+    /** @private */
+    advancedOpened_: {
+      type: Boolean,
+      value: false,
+      notify: true,
+    },
+
     /** @private {boolean} */
     toolbarSpinnerActive_: {
       type: Boolean,
       value: false,
     },
 
     /**
      * Dictionary defining page visibility.
      * @private {!GuestModePageVisibility}
      */
@@ skipping 76 matching lines @@
   onMenuButtonTap_: function() {
     this.$$('app-drawer').toggle();
   },
 
   /** @private */
   directionDelegateChanged_: function() {
     this.$$('app-drawer').align = this.directionDelegate.isRtl() ?
         'right' : 'left';
   },
 });