MD Settings: Custom expand/collapse section animations.

chrome/browser/resources/settings/advanced_page/advanced_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-advanced-page' is the settings page containing the advanced
  * settings.
  *
  * Example:
  *
  *    <iron-animated-pages>
  *      <settings-advanced-page prefs="{{prefs}}">
  *      </settings-advanced-page>
  *      ... other pages ...
  *    </iron-animated-pages>
  */
 Polymer({
   is: 'settings-advanced-page',
 
+  behaviors: [I18nBehavior, SettingsPageVisibility, RoutableBehavior],
+
   properties: {
     /**
      * Preferences state.
      */
     prefs: {
       type: Object,
       notify: true,
     },
 
     /**
      * The current active route.
      */
     currentRoute: {
       type: Object,
       notify: true,
     },
   },
 
+  /**
+   * @type {string} Selector to get the sections.
+   * TODO(michaelpg): replace duplicate docs with @override once b/24294625
+   * is fixed.
+   */
+  sectionSelector: 'settings-section',
+
 <if expr="not chromeos">
   listeners: {
     'dom-change': 'onDomChange_',
   },
+</if>
 
+  /** @override */
+  attached: function() {
+    /** @override */
+    this.scroller = this.parentElement;
+  },
+
+<if expr="not chromeos">
   /** @private */
   onDomChange_: function() {
     var systemPage = /** @type {?SettingsSystemPageElement} */(
         this.$$('settings-system-page'));
     if (systemPage && !systemPage.delegate)
       systemPage.delegate = new settings.SystemPageDelegateImpl;
   },
 </if>
-
-  behaviors: [I18nBehavior, SettingsPageVisibility],
 });