content: Cleanup class/struct forward declarations

content/browser/devtools/devtools_manager.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 CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_MANAGER_H_
 #define CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_MANAGER_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/devtools_manager_delegate.h"
 
 namespace content {
 
-class DevToolsAgentHostImpl;
 class DevToolsHttpHandler;
 
 // This class is a singleton that manage global DevTools state for the whole
 // browser.
 // TODO(dgozman): remove this class entirely.
 class CONTENT_EXPORT DevToolsManager {
  public:
   // Returns single instance of this class. The instance is destroyed on the
   // browser main loop exit so this method MUST NOT be called after that point.
   static DevToolsManager* GetInstance();
@@ skipping 10 matching lines @@
 
   std::unique_ptr<DevToolsManagerDelegate> delegate_;
   std::unique_ptr<DevToolsHttpHandler> http_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_MANAGER_H_