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

chrome/browser/resources/settings/languages_page/add_languages_dialog.js

Index: chrome/browser/resources/settings/languages_page/add_languages_dialog.js
diff --git a/chrome/browser/resources/settings/languages_page/add_languages_dialog.js b/chrome/browser/resources/settings/languages_page/add_languages_dialog.js
index dc0e2b8e707ea11a6dd3657108671648f664ccb4..591c91cf14f9a48b82c55256d5def4dadb545a44 100644
--- a/chrome/browser/resources/settings/languages_page/add_languages_dialog.js
+++ b/chrome/browser/resources/settings/languages_page/add_languages_dialog.js
@@ -63,7 +63,7 @@ Polymer({
    * @private
    */
   getLanguages_: function() {
-    return this.languages.supported.filter(function(language) {
+    return this.languages.supported.filter(language => {
       var isAvailableLanguage =
           !this.languageHelper.isLanguageEnabled(language.code);
 
@@ -75,7 +75,7 @@ Polymer({
 
       return language.displayName.toLowerCase().includes(
           this.filterValue_.toLowerCase());
-    }.bind(this));
+    });
   },
 
   /**
@@ -132,8 +132,8 @@ Polymer({
    */
   onActionButtonTap_: function() {
     this.$.dialog.close();
-    this.languagesToAdd_.forEach(function(languageCode) {
+    this.languagesToAdd_.forEach(languageCode => {
       this.languageHelper.enableLanguage(languageCode);
-    }.bind(this));
+    });
   },
 });