MD Settings: break SettingsPageUIHandler to its own file

chrome/browser/ui/webui/settings/languages_handler.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_LANGUAGES_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_LANGUAGES_HANDLER_H_
 
 #include "base/macros.h"
-#include "chrome/browser/ui/webui/settings/md_settings_ui.h"
+#include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
 
 namespace base {
 class ListValue;
 }
 
 namespace content {
 class WebUI;
 }
 
 class Profile;
@@ skipping 17 matching lines @@
   void HandleRestart(const base::ListValue* args);
 
   Profile* profile_;  // Weak pointer.
 
   DISALLOW_COPY_AND_ASSIGN(LanguagesHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_LANGUAGES_HANDLER_H_