MD Settings: reduce complexity and overhead of Languages singleton

chrome/browser/resources/settings/languages_page/manage_input_methods_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-manage-input-methods-page' is a sub-page for enabling
  * and disabling input methods. Input methods are grouped by base languages to
  * avoid showing duplicate or ambiguous input methods.
  *
  * @group Chrome Settings Elements
@@ skipping 21 matching lines @@
       value: function() { return []; },
     },
   },
 
   observers: [
     'availableInputMethodsChanged_(languages.enabled.*,' +
         'languages.inputMethods.supported.*)',
     'enabledInputMethodsChanged_(languages.inputMethods.enabled.*)',
   ],
 
-  /** @override */
-  created: function() {
-    this.languageHelper_ = LanguageHelperImpl.getInstance();
-  },
-
   /** @private */
   availableInputMethodsChanged_: function() {
     this.populateLanguageList_();
   },
 
   /** @private */
   enabledInputMethodsChanged_: function() {
     this.populateLanguageList_();
   },
 
   /**
    * Handler for an input method checkbox.
    * @param {!{model: !{item: chrome.languageSettingsPrivate.InputMethod},
    *           target: !PaperCheckboxElement}} e
    * @private
    */
   onCheckboxChange_: function(e) {
     // TODO(michaelpg): Show confirmation dialog for 3rd-party IMEs.
     var id = e.model.item.id;
     if (e.target.checked)
-      this.languageHelper_.addInputMethod(id);
+      settings.LanguageHelperImpl.getInstance().addInputMethod(id);
     else
-      this.languageHelper_.removeInputMethod(id);
+      settings.LanguageHelperImpl.getInstance().removeInputMethod(id);
   },
 
   /**
    * Returns true if the input method can be removed.
    * @param {!chrome.languageSettingsPrivate.InputMethod} targetInputMethod
    * @param {!Object} change Polymer change object (provided in the HTML so this
    *     gets called whenever languages.inputMethods.enabled.* changes).
    * @return {boolean}
    * @private
    */
   enableInputMethodCheckbox_: function(targetInputMethod, change) {
     if (!targetInputMethod.enabled)
       return true;
 
+    var languageHelper = settings.LanguageHelperImpl.getInstance();
+
     // Third-party IMEs can always be removed.
-    if (!this.languageHelper_.isComponentIme(targetInputMethod))
+    if (!languageHelper.isComponentIme(targetInputMethod))
       return true;
 
     // Can be removed as long as there is another component IME.
     return this.languages.inputMethods.enabled.some(function(inputMethod) {
       return inputMethod != targetInputMethod &&
-          this.languageHelper_.isComponentIme(inputMethod);
+          languageHelper.isComponentIme(inputMethod);
     }, this);
   },
 
   /**
    * Creates the list of languages and their input methods as the data source
    * for the view.
    * @private
    */
   populateLanguageList_: function() {
     var languageList = [];
+    var languageHelper = settings.LanguageHelperImpl.getInstance();
 
     // Languages that have already been listed further up.
     var /** !Set<string> */ usedLanguages = new Set();
 
     // Add languages in preference order. However, if there are multiple
     // enabled variants of the same base language, group them all as the base
     // language instead of showing each variant individually. This prevents us
     // from displaying duplicate input methods under different variants.
     for (var i = 0; i < this.languages.enabled.length; i++) {
       var languageState = this.languages.enabled[i];
       // Skip the language if we have already included it or its base language.
       if (usedLanguages.has(languageState.language.code))
         continue;
-      var baseLanguageCode = this.languageHelper_.getLanguageCodeWithoutRegion(
+      var baseLanguageCode = languageHelper.getLanguageCodeWithoutRegion(
           languageState.language.code);
       if (usedLanguages.has(baseLanguageCode))
         continue;
 
       // Find the other languages further down in the preferred languages list
       // which also use this language's base language code.
       var languageFamilyCodes = [languageState.language.code];
       for (var j = i + 1; j < this.languages.enabled.length; j++) {
         var otherCode = this.languages.enabled[j].language.code;
-        if (this.languageHelper_.getLanguageCodeWithoutRegion(otherCode) ==
+        if (languageHelper.getLanguageCodeWithoutRegion(otherCode) ==
             baseLanguageCode) {
           languageFamilyCodes.push(this.languages.enabled[j].language.code);
         }
       }
 
       var combinedInputMethods =
           this.getInputMethodsForLanguages(languageFamilyCodes);
 
       // Skip the language if it has no new input methods.
       if (!combinedInputMethods.length)
         continue;
 
       // Add the language or base language.
       var displayLanguage = languageState.language;
       if (languageFamilyCodes.length > 1) {
-        var baseLanguage = this.languageHelper_.getLanguage(baseLanguageCode);
+        var baseLanguage = languageHelper.getLanguage(baseLanguageCode);
         if (baseLanguage)
           displayLanguage = baseLanguage;
       }
       languageList.push({
         language: displayLanguage,
         inputMethods: combinedInputMethods,
       });
       for (var languageCode of languageFamilyCodes)
         usedLanguages.add(languageCode);
     }
 
     this.languageList_ = languageList;
     this.notifyInputMethodsChanged_();
   },
 
   /**
    * Returns the input methods that support any of the given languages.
    * @param {!Array<string>} languageCodes
    * @return {!Array<!chrome.languageSettingsPrivate.InputMethod>}
    * @private
    */
   getInputMethodsForLanguages: function(languageCodes) {
     // Input methods that have already been listed for this language.
     var /** !Set<string> */ usedInputMethods = new Set();
     /** @type {!Array<chrome.languageSettingsPrivate.InputMethod>} */
     var combinedInputMethods = [];
     for (var languageCode of languageCodes) {
-      var inputMethods = this.languageHelper_.getInputMethodsForLanguage(
-          languageCode);
+      var inputMethods =
+          settings.LanguageHelperImpl.getInstance().getInputMethodsForLanguage(
+              languageCode);
       // Get the language's unused input methods and mark them as used.
       var newInputMethods = inputMethods.filter(function(inputMethod) {
         if (usedInputMethods.has(inputMethod.id))
           return false;
         usedInputMethods.add(inputMethod.id);
         return true;
       });
       [].push.apply(combinedInputMethods, newInputMethods);
     }
     return combinedInputMethods;
   },
 
   // TODO(Polymer/polymer#3603): We have to notify Polymer of properties that
   // may have changed on nested objects, even when the outer property itself
   // is set to a new array.
   // TODO(michaelpg): Test this behavior.
   /** @private */
   notifyInputMethodsChanged_: function() {
     for (var i = 0; i < this.languageList_.length; i++) {
       for (var j = 0; j < this.languageList_[i].inputMethods.length; j++) {
         this.notifyPath(
             'languageList_.' + i + '.inputMethods.' + j + '.enabled',
             this.languageList_[i].inputMethods[j].enabled);
       }
     }
   },
 });