Clean forward declaration in public

public/platform/WebSpeechSynthesizer.h

 /*
  * Copyright (C) 2013 Google 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
@@ skipping 12 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebSpeechSynthesizer_h
 #define WebSpeechSynthesizer_h
 
 #include "WebCommon.h"
 
 namespace blink {
 
-class WebSpeechSynthesizerClient;
 class WebSpeechSynthesisUtterance;
 
 class WebSpeechSynthesizer {
 public:
     virtual ~WebSpeechSynthesizer() { }
 
     virtual void updateVoiceList() = 0;
 
     // OK to call with more than one utterance, will queue.
     virtual void speak(const WebSpeechSynthesisUtterance&) = 0;
 
     virtual void pause() = 0;
     virtual void resume() = 0;
     virtual void cancel() = 0;
 };
 
 } // namespace blink
 
 #endif // WebSpeechSynthesizer_h