chrome: Cleanup class/struct forward declarations

chrome/browser/ui/webui/ntp/core_app_launcher_handler.h

 // Copyright 2013 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_NTP_CORE_APP_LAUNCHER_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_CORE_APP_LAUNCHER_HANDLER_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/values.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "content/public/browser/web_ui_message_handler.h"
 #include "extensions/common/extension.h"
 
-namespace extensions {
-class Extension;
-}
-
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 class Profile;
 
 class CoreAppLauncherHandler : public content::WebUIMessageHandler {
  public:
   CoreAppLauncherHandler();
   ~CoreAppLauncherHandler() override;
@@ skipping 13 matching lines @@
                             std::string escaped_url,
                             extension_misc::AppLaunchBucket bucket);
 
   // WebUIMessageHandler implementation.
   void RegisterMessages() override;
 
   DISALLOW_COPY_AND_ASSIGN(CoreAppLauncherHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NTP_CORE_APP_LAUNCHER_HANDLER_H_