MD Settings: Remove some unhelpful properties

chrome/browser/resources/settings/settings_page/main_page_behavior.js

 // Copyright 2016 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.
 
 // Fast out, slow in.
 var EASING_FUNCTION = 'cubic-bezier(0.4, 0, 0.2, 1)';
 var EXPAND_DURATION = 350;
 
 /**
  * Calls |readyTest| repeatedly until it returns true, then calls
@@ skipping 12 matching lines @@
   }, 10);
 }
 
 /**
  * Provides animations to expand and collapse individual sections in a page.
  * Expanded sections take up the full height of the container. At most one
  * section should be expanded at any given time.
  * @polymerBehavior Polymer.MainPageBehavior
  */
 var MainPageBehaviorImpl = {
-  /**
-   * @type {string} Selector to get the sections. Derived elements
-   *     must override.
-   */
-  sectionSelector: '',
-
   /** @type {?Element} The scrolling container. */
   scroller: null,
 
   /** @override */
   attached: function() {
     if (this.domHost && this.domHost.parentNode.tagName == 'PAPER-HEADER-PANEL')
       this.scroller = this.domHost.parentNode.$.mainContainer;
     else
       this.scroller = document.body; // Used in unit tests.
   },
 
   /**
    * Hides or unhides the sections not being expanded.
    * @param {string} sectionName The section to keep visible.
    * @param {boolean} hidden Whether the sections should be hidden.
    * @private
    */
   toggleOtherSectionsHidden_: function(sectionName, hidden) {
     var sections = Polymer.dom(this.root).querySelectorAll(
-        this.sectionSelector);
+        'settings-section');
     for (var section of sections)
       section.hidden = hidden && (section.section != sectionName);
   },
 
   /**
    * Animates the card in |section|, expanding it to fill the page.
    * @param {!SettingsSectionElement} section
    */
   expandSection: function(section) {
     // If another section's card is expanding, cancel that animation first.
@@ skipping 358 matching lines @@
         this.$$('[section=' + section + ']'));
   },
 };
 
 
 /** @polymerBehavior */
 var RoutableBehavior = [
   MainPageBehavior,
   RoutableBehaviorImpl
 ];