MD Settings: Custom expand/collapse section animations.

chrome/browser/resources/settings/basic_page/basic_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-basic-page' is the settings page containing the basic settings.
  *
  * Example:
  *
@@ skipping 28 matching lines @@
      */
     showResetProfileBanner_: {
       type: Boolean,
       value: function() {
         return loadTimeData.getBoolean('showResetProfileBanner');
       },
     },
 
   },
 
-  behaviors: [I18nBehavior, SettingsPageVisibility],
+  /**
+   * @type {string} Selector to get the sections.
+   * TODO(michaelpg): replace duplicate docs with @override once b/24294625
+   * is fixed.
+   */
+  sectionSelector: 'settings-section',
+
+  /** @override */
+  attached: function() {
+    /** @override */
+    this.scroller = this.parentElement;
+  },
+
+  behaviors: [I18nBehavior, SettingsPageVisibility, RoutableBehavior],
 
   onResetDone_: function() {
     this.showResetProfileBanner_ = false;
   },
 });