chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/api/messaging/native_message_port.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_MESSAGING_NATIVE_MESSAGE_PORT_H_
 #define CHROME_BROWSER_EXTENSIONS_API_MESSAGING_NATIVE_MESSAGE_PORT_H_
 
 #include "base/threading/thread_checker.h"
 #include "chrome/browser/extensions/api/messaging/message_service.h"
 
 namespace extensions {
-class NativeMessageProcessHost;
 
 // A port that manages communication with a native application.
 // All methods must be called on the UI Thread of the browser process.
 class NativeMessagePort : public MessageService::MessagePort {
  public:
   NativeMessagePort(base::WeakPtr<MessageService> message_service,
                     int port_id,
                     std::unique_ptr<NativeMessageHost> native_message_host);
   ~NativeMessagePort() override;
 
@@ skipping 11 matching lines @@
   scoped_refptr<base::SingleThreadTaskRunner> host_task_runner_;
   int port_id_;
   std::unique_ptr<Core> core_;
 
   base::WeakPtrFactory<NativeMessagePort> weak_factory_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_MESSAGING_NATIVE_MESSAGE_PORT_H_