content: Cleanup class/struct forward declarations

content/child/webmessageportchannel_impl.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_CHILD_WEBMESSAGEPORTCHANNEL_IMPL_H_
 #define CONTENT_CHILD_WEBMESSAGEPORTCHANNEL_IMPL_H_
 
 #include <memory>
 #include <queue>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string16.h"
 #include "base/synchronization/lock.h"
 #include "ipc/ipc_listener.h"
 #include "third_party/WebKit/public/platform/WebMessagePortChannel.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace content {
-class ChildThread;
 
 // This is thread safe.
 class WebMessagePortChannelImpl
     : public blink::WebMessagePortChannel,
       public IPC::Listener,
       public base::RefCountedThreadSafe<WebMessagePortChannelImpl> {
  public:
   explicit WebMessagePortChannelImpl(
       const scoped_refptr<base::SingleThreadTaskRunner>&
           main_thread_task_runner);
@@ skipping 86 matching lines @@
   int route_id_;  // The routing id for this object.
   int message_port_id_;  // A globally unique identifier for this message port.
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(WebMessagePortChannelImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBMESSAGEPORTCHANNEL_IMPL_H_