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

chrome/browser/resources/settings/languages_page/languages_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-languages-page' is the settings page
  * for language and input method settings.
  */
 cr.exportPath('settings');
 
@@ skipping 78 matching lines @@
    * Stamps and opens the Add Languages dialog, registering a listener to
    * disable the dialog's dom-if again on close.
    * @param {!Event} e
    * @private
    */
   onAddLanguagesTap_: function(e) {
     e.preventDefault();
     this.showAddLanguagesDialog_ = true;
     this.async(function() {
       var dialog = this.$$('settings-add-languages-dialog');
-      dialog.addEventListener('close', function() {
+      dialog.addEventListener('close', () => {
         this.showAddLanguagesDialog_ = false;
         cr.ui.focusWithoutInk(assert(this.$.addLanguages));
-      }.bind(this));
+      });
     });
   },
 
   /**
    * Used to determine which "Move" buttons to show for ordering enabled
    * languages.
    * @param {number} n
    * @param {!LanguageState} language
    * @return {boolean} True if |language| is at the |n|th index in the list of
    *     enabled languages.
@@ skipping 451 matching lines @@
     if (e.target.tagName == expandButtonTag)
       return;
 
     /** @type {!CrExpandButtonElement} */
     var expandButton = e.currentTarget.querySelector(expandButtonTag);
     assert(expandButton);
     expandButton.expanded = !expandButton.expanded;
   },
 });
 })();