Cleanup: Remove some unneeded Extension* class forward declarations.

chrome/browser/extensions/api/developer_private/developer_private_api.h

 // Copyright (c) 2012 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_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_API_H_
 
 #include <set>
 
 #include "base/files/file.h"
 #include "chrome/browser/extensions/api/developer_private/entry_picker.h"
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/browser/extensions/error_console/error_console.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/extension_uninstall_dialog.h"
 #include "chrome/browser/extensions/pack_extension_job.h"
 #include "chrome/browser/extensions/requirements_checker.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/render_view_host.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
 #include "extensions/browser/event_router.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
 #include "webkit/browser/fileapi/file_system_context.h"
 #include "webkit/browser/fileapi/file_system_operation.h"
 
-class ExtensionService;
 class Profile;
 
 namespace extensions {
 
 class ExtensionError;
 class ExtensionSystem;
 class ManagementPolicy;
 
 namespace api {
 
@@ skipping 422 matching lines @@
 
   // ExtensionFunction:
   virtual bool RunAsync() OVERRIDE;
 };
 
 }  // namespace api
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_API_H_