Add [WillBeGarbageCollected] to Event.idl

Source/modules/mediastream/MediaStreamEvent.h

Index: Source/modules/mediastream/MediaStreamEvent.h
diff --git a/Source/modules/mediastream/MediaStreamEvent.h b/Source/modules/mediastream/MediaStreamEvent.h
index fc646fb3e2d0afed0cb4ecec759d5b467fb555ee..1c863ca015fcf44bd3127a6b185bbc4f18e57e13 100644
--- a/Source/modules/mediastream/MediaStreamEvent.h
+++ b/Source/modules/mediastream/MediaStreamEvent.h
@@ -41,9 +41,9 @@ class MediaStreamEvent FINAL : public Event {
 public:
     virtual ~MediaStreamEvent();
 
-    static PassRefPtr<MediaStreamEvent> create();
-    static PassRefPtr<MediaStreamEvent> create(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtr<MediaStream>);
-    static PassRefPtr<MediaStreamEvent> create(const AtomicString& type, const MediaStreamEventInit& initializer);
+    static PassRefPtrWillBeRawPtr<MediaStreamEvent> create();
+    static PassRefPtrWillBeRawPtr<MediaStreamEvent> create(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtr<MediaStream>);
+    static PassRefPtrWillBeRawPtr<MediaStreamEvent> create(const AtomicString& type, const MediaStreamEventInit& initializer);
 
     MediaStream* stream() const;
     MediaStream* stream(bool&) const;