Make NotificationEvent constructable.

Source/modules/notifications/NotificationEvent.h

Index: Source/modules/notifications/NotificationEvent.h
diff --git a/Source/modules/notifications/NotificationEvent.h b/Source/modules/notifications/NotificationEvent.h
index 8921acf060009b125dad876ee40f2a02d8a701ab..048c098f45bef2a29ac8d3165801746e79f18b13 100644
--- a/Source/modules/notifications/NotificationEvent.h
+++ b/Source/modules/notifications/NotificationEvent.h
@@ -12,7 +12,7 @@
 
 namespace blink {
 
-struct NotificationEventInit : public EventInit {
+struct NotificationEventInit : public ExtendableEventInit {
     NotificationEventInit();
 
     Member<Notification> notification;
@@ -25,6 +25,10 @@ public:
     {
         return adoptRefWillBeNoop(new NotificationEvent);
     }
+    static PassRefPtrWillBeRawPtr<NotificationEvent> create(const AtomicString& type, const NotificationEventInit& initializer)
+    {
+        return adoptRefWillBeNoop(new NotificationEvent(type, initializer));
+    }
     static PassRefPtrWillBeRawPtr<NotificationEvent> create(const AtomicString& type, const NotificationEventInit& initializer, WaitUntilObserver* observer)
     {
         return adoptRefWillBeNoop(new NotificationEvent(type, initializer, observer));
@@ -40,6 +44,7 @@ public:
 
 private:
     NotificationEvent();
+    NotificationEvent(const AtomicString& type, const NotificationEventInit&);
     NotificationEvent(const AtomicString& type, const NotificationEventInit&, WaitUntilObserver*);
 
     PersistentWillBeMember<Notification> m_notification;