Remove unnecessary includes from dom.

third_party/WebKit/Source/core/dom/MessageChannel.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 #ifndef MessageChannel_h
 #define MessageChannel_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
-#include "wtf/RefPtr.h"
 
 namespace blink {
 
 class MessagePort;
 class ExecutionContext;
 
 class MessageChannel final : public GarbageCollectedFinalized<MessageChannel>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static MessageChannel* create(ExecutionContext* context)
     {
         return new MessageChannel(context);
     }
 
     MessagePort* port1() const { return m_port1; }
     MessagePort* port2() const { return m_port2; }
 
     DECLARE_TRACE();
 
 private:
     explicit MessageChannel(ExecutionContext*);
 
     Member<MessagePort> m_port1;
     Member<MessagePort> m_port2;
 };
 
 } // namespace blink
 
 #endif // MessageChannel_h