Add [WillBeGarbageCollected] to Event.idl

Source/core/events/BeforeTextInsertedEvent.h

Index: Source/core/events/BeforeTextInsertedEvent.h
diff --git a/Source/core/events/BeforeTextInsertedEvent.h b/Source/core/events/BeforeTextInsertedEvent.h
index fe0f3f7c27c867b48da8abc2fd8d5bf50688fba8..5cba43ffb6cbebe62f9d949c25e7beab583cfe59 100644
--- a/Source/core/events/BeforeTextInsertedEvent.h
+++ b/Source/core/events/BeforeTextInsertedEvent.h
@@ -34,9 +34,9 @@ class BeforeTextInsertedEvent FINAL : public Event {
 public:
     virtual ~BeforeTextInsertedEvent();
 
-    static PassRefPtr<BeforeTextInsertedEvent> create(const String& text)
+    static PassRefPtrWillBeRawPtr<BeforeTextInsertedEvent> create(const String& text)
     {
-        return adoptRef(new BeforeTextInsertedEvent(text));
+        return adoptRefCountedWillBeRefCountedGarbageCollected(new BeforeTextInsertedEvent(text));
     }
 
     virtual const AtomicString& interfaceName() const OVERRIDE;