Add an option in language settings for activating the IME menu.

chrome/browser/resources/options/language_options.js

 // Copyright (c) 2012 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.
 
 // TODO(kochi): Generalize the notification as a component and put it
 // in js/cr/ui/notification.js .
 
 cr.define('options', function() {
   /** @const */ var Page = cr.ui.pageManager.Page;
   /** @const */ var PageManager = cr.ui.pageManager.PageManager;
@@ skipping 48 matching lines @@
    */
   var SPELL_CHECK_DICTIONARIES_PREF = 'spellcheck.dictionaries';
 
   /**
    * The preference that indicates if the Translate feature is enabled.
    * @type {string}
    * @const
    */
   var ENABLE_TRANSLATE = 'translate.enabled';
 
+  /**
+   * The preference is a boolean that activates/deactivates IME menu on shelf.
+   * @type {string}
+   * @const
+   */
+  var ACTIVATE_IME_MENU_PREF = 'settings.language.ime_menu_activated';
+
   /////////////////////////////////////////////////////////////////////////////
   // LanguageOptions class:
 
   /**
    * Encapsulated handling of ChromeOS language options page.
    * @constructor
    * @extends {cr.ui.pageManager.Page}
    */
   function LanguageOptions(model) {
     Page.call(this, 'languages',
@@ skipping 184 matching lines @@
           chrome.send('uiLanguageRestart');
         };
       }
 
       $('language-confirm').onclick =
           PageManager.closeOverlay.bind(PageManager);
 
       // Public session users cannot change the locale.
       if (cr.isChromeOS && UIAccountTweaks.loggedInAsPublicAccount())
         $('language-options-ui-language-section').hidden = true;
+
+      if (loadTimeData.getBoolean('enableLanguageOptionsImeMenu')) {
+        $('language-options-ime-menu-template').hidden = false;
+      }
+
+      // Listen to check on 'activate-ime-menu' checkbox
+      var checkboxImeMenu = $('activate-ime-menu');
+      checkboxImeMenu.addEventListener('click',
+          this.handleActivateImeMenuCheckboxClick_.bind(this));
     },
 
     /**
      * Initializes the input method list.
      */
     initializeInputMethodList_: function() {
       var inputMethodList = $('language-options-input-method-list');
       var inputMethodPrototype = $('language-options-input-method-template');
 
       // Add all input methods, but make all of them invisible here. We'll
@@ skipping 1126 matching lines @@
       if (main in synonyms) {
         return synonyms[main];
       } else if (main == 'zh') {
         // In Translation, general Chinese is not used, and the sub code is
         // necessary as a language code for Translate server.
         return languageCode;
       }
 
       return main;
     },
+
+    /**
+     * Handles activate-ime-menu checkbox's click event.
+     * @param {Event} e Click event.
+     * @private
+     */
+    handleActivateImeMenuCheckboxClick_: function(e) {
+      var checkbox = e.target;
+      Preferences.setBooleanPref(ACTIVATE_IME_MENU_PREF,
+        checkbox.checked, true);

[stevenjb, 2016/01/05 17:31:13]

The preferred format is to align the arguments, i.e.
       Preferences.setBooleanPref(ACTIVATE_IME_MENU_PREF,
                                  checkbox.checked, true);

(Originally 'checkbox' was aligned with '(' instead of 'A')

[Azure Wei, 2016/01/07 03:04:57]

Done.

+    },
   };
 
   /**
    * Shows the node at |index| in |nodes|, hides all others.
    * @param {Array<HTMLElement>} nodes The nodes to be shown or hidden.
    * @param {number} index The index of |nodes| to show.
    */
   function showMutuallyExclusiveNodes(nodes, index) {
     assert(index >= 0 && index < nodes.length);
     for (var i = 0; i < nodes.length; ++i) {
@@ skipping 16 matching lines @@
 
   LanguageOptions.onDictionaryDownloadFailure = function(languageCode) {
     LanguageOptions.getInstance().onDictionaryDownloadFailure_(languageCode);
   };
 
   // Export
   return {
     LanguageOptions: LanguageOptions
   };
 });