MD Settings: Remove some ES6 leftovers from CrOS code that break uglify.

chrome/browser/resources/settings/device_page/device_page.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.
 
 /**
  * @fileoverview 'settings-device-page' is the settings page for device and
  * peripheral settings.
  */
 Polymer({
   is: 'settings-device-page',
@@ skipping 201 matching lines @@
       return source.type == settings.PowerDeviceType.DUAL_ROLE_USB;
     });
   },
 
   /**
    * @param {!Array<!settings.PowerSource>} powerSources
    * @param {boolean} lowPowerCharger
    * @return {string} Description of the power source.
    * @private
    */
-  computePowerSourceName_(powerSources, lowPowerCharger) {
+  computePowerSourceName_: function (powerSources, lowPowerCharger) {
     if (lowPowerCharger)
       return this.i18n('powerSourceLowPowerCharger');
     if (powerSources.length)
       return this.i18n('powerSourceAcAdapter');
     return '';
   },
 
   /**
    * Handler for tapping the mouse and touchpad settings menu item.
    * @private
@@ skipping 72 matching lines @@
    * @private
    */
   checkPointerSubpage_: function() {
     // Check that the properties have explicitly been set to false.
     if (this.hasMouse_ === false && this.hasTouchpad_ === false &&
         settings.getCurrentRoute() == settings.Route.POINTERS) {
       settings.navigateTo(settings.Route.DEVICE);
     }
   },
 });