MD Settings: break SettingsPageUIHandler to its own file

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

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_SITE_SETTINGS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_SITE_SETTINGS_HANDLER_H_
 
 #include <vector>
 
 #include "chrome/browser/storage/storage_info_fetcher.h"
-#include "chrome/browser/ui/webui/settings/md_settings_ui.h"
+#include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
 
 class Profile;
 
 namespace base {
 class ListValue;
 }
 
 namespace settings {
 
 // Chrome "ContentSettings" settings page UI handler.
@@ skipping 27 matching lines @@
 
   // The origin for which to clear usage.
   std::string clearing_origin_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteSettingsHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_SITE_SETTINGS_HANDLER_H_