Extract language settings methods into a LanguageHelper interface

chrome/browser/resources/settings/languages_page/manage_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-manage-languages-page' is a sub-page for enabling
  * and disabling languages.
  *
  * @group Chrome Settings Elements
  * @element settings-manage-languages-page
@@ skipping 19 matching lines @@
     },
 
     /**
      * @private {!Array<!{code: string, displayName: string,
      *                    nativeDisplayName: string, enabled: boolean}>|
      *           undefined}
      */
     availableLanguages_: Array,
   },
 
+  /** @private {!LanguageHelper} */
+  languageHelper_: LanguageHelperImpl.getInstance(),
+
   observers: [
     'enabledLanguagesChanged_(languages.enabledLanguages.*)',
   ],
 
   /**
    * Handler for removing a language.
    * @param {!{model: !{item: !LanguageInfo}}} e
    * @private
    */
   onRemoveLanguageTap_: function(e) {
-    this.$.languages.disableLanguage(e.model.item.language.code);
+    this.languageHelper_.disableLanguage(e.model.item.language.code);
   },
 
   /**
    * Handler for adding a language.
    * @param {!{model: {item: !chrome.languageSettingsPrivate.Language}}} e
    * @private
    */
   onAddLanguageTap_: function(e) {
-    this.$.languages.enableLanguage(e.model.item.code);
+    this.languageHelper_.enableLanguage(e.model.item.code);
   },
 
   /**
    * True if a language is not the current or prospective UI language.
    * @param {string} languageCode
-   * @param {!Array<!LanguageInfo>} prospectiveUILanguage
+   * @param {string} prospectiveUILanguageCode
    * @return {boolean}
    * @private
    */
-  canRemoveLanguage_: function(languageCode, prospectiveUILanguage) {
+  canRemoveLanguage_: function(languageCode, prospectiveUILanguageCode) {
     if (languageCode == navigator.language ||
-        languageCode == prospectiveUILanguage) {
+        languageCode == prospectiveUILanguageCode) {
       return false;
     }
     assert(this.languages.enabledLanguages.length > 1);
     return true;
   },
 
   /**
    * Updates the available languages that are bound to the iron-list.
    * @private
    */
   enabledLanguagesChanged_: function() {
     if (!this.availableLanguages_) {
       var availableLanguages = [];
       for (var i = 0; i < this.languages.supportedLanguages.length; i++) {
         var language = this.languages.supportedLanguages[i];
         availableLanguages.push({
           code: language.code,
           displayName: language.displayName,
           nativeDisplayName: language.nativeDisplayName,
-          enabled: this.$.languages.isEnabled(language.code)
+          enabled: this.languageHelper_.isLanguageEnabled(language.code),
         });
       }
       // Set the Polymer property after building the full array.
       this.availableLanguages_ = availableLanguages;
     } else {
       // Update the available languages in place.
       for (var i = 0; i < this.availableLanguages_.length; i++) {
         this.set('availableLanguages_.' + i + '.enabled',
-                 this.$.languages.isEnabled(this.availableLanguages_[i].code));
+                 this.languageHelper_.isLanguageEnabled(
+                      this.availableLanguages_[i].code));
       }
     }
   },
 });