Oilpan: make DOMWindowProperty a GC mixin.

Source/core/css/StyleMedia.cpp

 /*
  * Copyright (C) 2009 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 49 matching lines @@
         return false;
 
     RefPtrWillBeRawPtr<MediaQuerySet> media = MediaQuerySet::create();
     if (!media->set(query))
         return false;
 
     MediaQueryEvaluator screenEval(m_frame);
     return screenEval.eval(media.get());
 }
 
+void StyleMedia::trace(Visitor* visitor)
+{
+    DOMWindowProperty::trace(visitor);
+}
+
 } // namespace blink