Switch speech synthesis from compile-flag to runtime-flag.

Source/core/platform/PlatformSpeechSynthesis.h

 /*
  * Copyright (C) 2013 Apple Computer, 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
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  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
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 #ifndef PlatformSpeechSynthesis_h
 #define PlatformSpeechSynthesis_h
 
-#if ENABLE(SPEECH_SYNTHESIS)
-
 #include <wtf/PassRefPtr.h>
 #include <wtf/RefCounted.h>
 #include <wtf/Vector.h>
 
 namespace WebCore {
     
 class SpeechSynthesis;
 class SpeechSynthesisUtterance;
 class SpeechSynthesisVoice;
     
 class PlatformSpeechSynthesis : public RefCounted<PlatformSpeechSynthesis> {
 public:
     static PassRefPtr<PlatformSpeechSynthesis> create(SpeechSynthesis*);
     
     void platformInitializeVoiceList(Vector<RefPtr<SpeechSynthesisVoice> >&);
     void platformSpeak(SpeechSynthesisUtterance*);
     
 private:
     PlatformSpeechSynthesis(SpeechSynthesis*);
 
     SpeechSynthesis* m_speechSynthesis;
 };
     
 } // namespace WebCore
 
-#endif // ENABLE(SPEECH_SYNTHESIS)
-
 #endif // PlatformSpeechSynthesis_h