Implement "Display Chrome OS in this language" button.

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/dom_ui/options_ui.h"
 
 class DictionaryValue;
 class ListValue;
 
 // 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:
-  // Get the list of input methods.
+  // Gets the list of input methods. The return value will look like:
+  // [{'id': 'pinyin', 'displayName': 'Pinyin', 'languageCode': 'zh-CW'}, ...]
   ListValue* GetInputMethodList();
 
-  // Get the list of languages.
+  // Gets the list of languages. The return value will look like:
+  // [{'code': 'fr', 'displayName': 'French'}, ...]
   ListValue* GetLanguageList();
 
+  // 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);
 };
 
 #endif  // CHROME_BROWSER_CHROMEOS_DOM_UI_LANGUAGE_OPTIONS_HANDLER_H_