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

Source/modules/mediastream/MediaStreamTrack.h

Index: Source/modules/mediastream/MediaStreamTrack.h
diff --git a/Source/modules/mediastream/MediaStreamTrack.h b/Source/modules/mediastream/MediaStreamTrack.h
index af79c06c575f3db6a5c1eee80af9e29c26e7e2be..f6f60266626557fa964e80dd9eda37516dcf96f1 100644
--- a/Source/modules/mediastream/MediaStreamTrack.h
+++ b/Source/modules/mediastream/MediaStreamTrack.h
@@ -45,8 +45,9 @@ class ExceptionState;
 class MediaStreamComponent;
 class MediaStreamTrackSourcesCallback;
 
-class MediaStreamTrack FINAL : public RefCounted<MediaStreamTrack>, public ScriptWrappable, public ActiveDOMObject, public EventTargetWithInlineData, public MediaStreamSource::Observer {
+class MediaStreamTrack FINAL : public RefCountedWillBeRefCountedGarbageCollected<MediaStreamTrack>, public ScriptWrappable, public ActiveDOMObject, public EventTargetWithInlineData, public MediaStreamSource::Observer {
     REFCOUNTED_EVENT_TARGET(MediaStreamTrack);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(MediaStreamTrack);
 public:
     class Observer {
     public: