Update chrome://device-emulator with newer Polymer guidelines

chrome/browser/resources/chromeos/emulator/device_emulator.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.
-
-cr.define('device_emulator', function() {
-  'use strict';
-
-  var audioSettings = $('audio-settings');
-  var batterySettings = $('battery-settings');
-  var bluetoothSettings = $('bluetooth-settings');
-
-  function initialize() {
-    audioSettings.initialize();
-    batterySettings.initialize();
-    bluetoothSettings.initialize();
-
-    var toggles = document.getElementsByClassName('menu-item-toggle');
-    for (var i = 0; i < toggles.length; ++i) {
-        toggles[i].addEventListener('click', handleDrawerItemClick);
-    }
-  }
-
-  /**
-   * Shows/hides a sidebar elements designated content.
-   * The content is identified by the |data-content-id| attribute of the
-   * sidebar element. This value is the ID of the HTML element to be toggled.
-   * @param {Event} e Contains information about the event which was fired.
-   */
-  function handleDrawerItemClick(e) {
-    var contentId = e.target.dataset.contentId;
-    var card = $(contentId);
-    card.hidden = !card.hidden;
-  }
-
-  // Return an object with all of the exports.
-  return {
-    initialize: initialize,
-    audioSettings: audioSettings,
-    batterySettings: batterySettings,
-    bluetoothSettings: bluetoothSettings,
-  };
-});
-
-document.addEventListener('DOMContentLoaded', device_emulator.initialize);