Oilpan: Allocate all EventTarget derived types on the manged heap.

Source/modules/webaudio/AudioContext.h

Index: Source/modules/webaudio/AudioContext.h
diff --git a/Source/modules/webaudio/AudioContext.h b/Source/modules/webaudio/AudioContext.h
index 7b0aec2d5b0bf7ed237d21ba554a24ea0de60a20..b77f0f685b6ee0c18afc35ba8467ff0788f94d1a 100644
--- a/Source/modules/webaudio/AudioContext.h
+++ b/Source/modules/webaudio/AudioContext.h
@@ -76,13 +76,14 @@ class WaveShaperNode;
 
 class AudioContext : public ThreadSafeRefCountedWillBeThreadSafeRefCountedGarbageCollected<AudioContext>, public ActiveDOMObject, public ScriptWrappable, public EventTargetWithInlineData {
     DEFINE_EVENT_TARGET_REFCOUNTING(ThreadSafeRefCountedWillBeThreadSafeRefCountedGarbageCollected<AudioContext>);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(AudioContext);
 public:
     // Create an AudioContext for rendering to the audio hardware.
     static PassRefPtrWillBeRawPtr<AudioContext> create(Document&, ExceptionState&);
 
     virtual ~AudioContext();
 
-    virtual void trace(Visitor*);
+    virtual void trace(Visitor*) OVERRIDE;
 
     bool isInitialized() const;
     // The constructor of an AudioNode must call this to initialize the context.