Oilpan: make DOMWindowProperty a GC mixin.

Source/modules/speech/DOMWindowSpeechSynthesis.cpp

 /*
  * Copyright (C) 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 #include "core/frame/LocalFrame.h"
 #include "wtf/PassRefPtr.h"
 
 namespace blink {
 
 DOMWindowSpeechSynthesis::DOMWindowSpeechSynthesis(LocalDOMWindow& window)
     : DOMWindowProperty(window.frame())
 {
 }
 
-DOMWindowSpeechSynthesis::~DOMWindowSpeechSynthesis()
-{
-}
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(DOMWindowSpeechSynthesis);
 
 const char* DOMWindowSpeechSynthesis::supplementName()
 {
     return "DOMWindowSpeechSynthesis";
 }
 
 // static
 DOMWindowSpeechSynthesis& DOMWindowSpeechSynthesis::from(LocalDOMWindow& window)
 {
     DOMWindowSpeechSynthesis* supplement = static_cast<DOMWindowSpeechSynthesis*>(WillBeHeapSupplement<LocalDOMWindow>::from(window, supplementName()));
@@ skipping 14 matching lines @@
 {
     if (!m_speechSynthesis && frame())
         m_speechSynthesis = SpeechSynthesis::create(frame()->domWindow()->executionContext());
     return m_speechSynthesis.get();
 }
 
 void DOMWindowSpeechSynthesis::trace(Visitor* visitor)
 {
     visitor->trace(m_speechSynthesis);
     WillBeHeapSupplement<LocalDOMWindow>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
 }
 
 } // namespace blink