Build the language list just like we do in the C++ version.

chrome/browser/chromeos/dom_ui/language_options_handler.h

 // Copyright (c) 2010 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_DOM_UI_LANGUAGE_OPTIONS_HANDLER_H_
 #define CHROME_BROWSER_CHROMEOS_DOM_UI_LANGUAGE_OPTIONS_HANDLER_H_
 #pragma once
 
+#include "chrome/browser/chromeos/input_method/input_method_util.h"
 #include "chrome/browser/dom_ui/options_ui.h"
 
 class DictionaryValue;
 class ListValue;
 
 namespace chromeos {
 
 // ChromeOS language options page UI handler.
 class LanguageOptionsHandler : public OptionsPageUIHandler {
  public:
   LanguageOptionsHandler();
   virtual ~LanguageOptionsHandler();
 
   // OptionsUIHandler implementation.
   virtual void GetLocalizedValues(DictionaryValue* localized_strings);
 
   // DOMMessageHandler implementation.
   virtual void RegisterMessages();
 
  private:
-  // Gets the list of input methods. The return value will look like:
+  // Gets the list of input methods from the given input descriptors.
+  // The return value will look like:
   // [{'id': 'pinyin', 'displayName': 'Pinyin', 'languageCode': 'zh-CW'}, ...]
-  ListValue* GetInputMethodList();
+  ListValue* GetInputMethodList(const InputMethodDescriptors& descriptors);
 
-  // Gets the list of languages. The return value will look like:
+  // Gets the list of languages from the given input descriptors.
+  // The return value will look like:
   // [{'code': 'fi', 'displayName': 'Finnish', 'nativeDisplayName': 'suomi'},
   //  ...]
-  ListValue* GetLanguageList();
+  ListValue* GetLanguageList(const InputMethodDescriptors& descriptors);
 
   // Called when the UI language is changed.
   // |value| will be the language code as string (ex. "fr").
   void UiLanguageChangeCallback(const Value* value);
 
   DISALLOW_COPY_AND_ASSIGN(LanguageOptionsHandler);
 };
 
 }  // namespace
 
 #endif  // CHROME_BROWSER_CHROMEOS_DOM_UI_LANGUAGE_OPTIONS_HANDLER_H_