Cleanup: Remove unneeded forward declarations from chrome/browser/extensions.

chrome/browser/extensions/extension_web_ui.h

 // Copyright (c) 2011 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_EXTENSIONS_EXTENSION_WEB_UI_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_WEB_UI_H_
 #pragma once
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/bookmarks/bookmark_manager_extension_api.h"
 #include "chrome/browser/favicon/favicon_service.h"
 #include "chrome/browser/ui/webui/chrome_web_ui.h"
 #include "chrome/common/extensions/extension.h"
 
 class GURL;
 class PrefService;
 class Profile;
-class RenderViewHost;
 class TabContents;
 
 namespace base {
 class ListValue;
 class Value;
 }
 
 // This class implements WebUI for extensions and allows extensions to put UI in
 // the main tab contents area. For example, each extension can specify an
 // "options_page", and that page is displayed in the tab contents area and is
@@ skipping 45 matching lines @@
   // TODO(aa): This seems out of place. Why is it not with the event routers for
   // the other extension APIs?
   scoped_ptr<BookmarkManagerExtensionEventRouter>
       bookmark_manager_extension_event_router_;
 
   // The URL this WebUI was created for.
   GURL url_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_WEB_UI_H_