Add [WillBeGarbageCollected] to Event.idl

Source/core/html/track/TrackEvent.h

Index: Source/core/html/track/TrackEvent.h
diff --git a/Source/core/html/track/TrackEvent.h b/Source/core/html/track/TrackEvent.h
index 15dc425464462c28cf2fe5fe2a8422864acd6ebf..f991bf1d60f19ff288e1ab156ee864d2509ec5c0 100644
--- a/Source/core/html/track/TrackEvent.h
+++ b/Source/core/html/track/TrackEvent.h
@@ -41,14 +41,14 @@ class TrackEvent FINAL : public Event {
 public:
     virtual ~TrackEvent();
 
-    static PassRefPtr<TrackEvent> create()
+    static PassRefPtrWillBeRawPtr<TrackEvent> create()
     {
-        return adoptRef(new TrackEvent);
+        return adoptRefWillBeRefCountedGarbageCollected(new TrackEvent);
     }
 
-    static PassRefPtr<TrackEvent> create(const AtomicString& type, const TrackEventInit& initializer)
+    static PassRefPtrWillBeRawPtr<TrackEvent> create(const AtomicString& type, const TrackEventInit& initializer)
     {
-        return adoptRef(new TrackEvent(type, initializer));
+        return adoptRefWillBeRefCountedGarbageCollected(new TrackEvent(type, initializer));
     }
 
     virtual const AtomicString& interfaceName() const OVERRIDE;