MD Settings: Convert all usages of .bind(this) to use ES6 arrow function.

chrome/browser/resources/settings/site_settings/category_default_setting.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
  * 'category-default-setting' is the polymer element for showing a certain
  * category under Site Settings.
  */
 Polymer({
@@ skipping 176 matching lines @@
     this.subControlParams_ = /** @type {chrome.settingsPrivate.PrefObject} */ (
         Object.assign({'value': subPrefValue}, basePref));
   },
 
   /**
    * Handles changes to the category pref and the |category| member variable.
    * @private
    */
   onCategoryChanged_: function() {
     this.browserProxy.getDefaultValueForContentType(this.category)
-        .then(function(defaultValue) {
+        .then(defaultValue => {
           this.updateControlParams_(defaultValue);
 
           // Flash only shows ALLOW or BLOCK descriptions on the toggle.
           var setting = defaultValue.setting;
           if (this.category == settings.ContentSettingsTypes.PLUGINS &&
               setting == settings.ContentSetting.IMPORTANT_CONTENT) {
             setting = settings.ContentSetting.ALLOW;
           } else if (
               this.category == settings.ContentSettingsTypes.COOKIES &&
               setting == settings.ContentSetting.SESSION_ONLY) {
             setting = settings.ContentSetting.ALLOW;
           }
           var categoryEnabled = setting != settings.ContentSetting.BLOCK;
           this.optionLabel_ =
               categoryEnabled ? this.toggleOnLabel : this.toggleOffLabel;
-        }.bind(this));
+        });
   },
 
   /**
    * @return {boolean}
    * @private
    */
   isToggleDisabled_: function() {
     return this.category == settings.ContentSettingsTypes.POPUPS &&
         loadTimeData.getBoolean('isGuest');
   },
 });