Extend PlatformSpeechSynthesizerMock with an utterance queue.

Source/modules/speech/SpeechSynthesisUtterance.cpp

 /*
  * Copyright (C) 2013 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 38 matching lines @@
     return ContextLifecycleObserver::executionContext();
 }
 
 const AtomicString& SpeechSynthesisUtterance::interfaceName() const
 {
     return EventTargetNames::SpeechSynthesisUtterance;
 }
 
 SpeechSynthesisVoice* SpeechSynthesisUtterance::voice() const
 {
-    return m_voice.get();
+    return m_voice;
 }
 
 void SpeechSynthesisUtterance::setVoice(SpeechSynthesisVoice* voice)
 {
     // Cache our own version of the SpeechSynthesisVoice so that we don't have to do some lookup
     // to go from the platform voice back to the speech synthesis voice in the read property.
     m_voice = voice;
 
     if (voice)
         m_platformUtterance->setVoice(voice->platformVoice());
 }
 
 void SpeechSynthesisUtterance::trace(Visitor* visitor)
 {
     visitor->trace(m_platformUtterance);
     visitor->trace(m_voice);
     RefCountedGarbageCollectedEventTargetWithInlineData<SpeechSynthesisUtterance>::trace(visitor);
     ContextLifecycleObserver::trace(visitor);
 }
 
 } // namespace blink