Decouple FileSystem and WebSQL callbacks from VoidCallback and it non-refcounted

Source/modules/notifications/NotificationCenter.h

Index: Source/modules/notifications/NotificationCenter.h
diff --git a/Source/modules/notifications/NotificationCenter.h b/Source/modules/notifications/NotificationCenter.h
index 160f672e81bc5baa550ff3b2f2712b05dc9168b5..14c479f33aa855c3647e88d099abc16919e06307 100644
--- a/Source/modules/notifications/NotificationCenter.h
+++ b/Source/modules/notifications/NotificationCenter.h
@@ -68,7 +68,7 @@ public:
     NotificationClient* client() const { return m_client; }
 
     int checkPermission();
-    void requestPermission(PassRefPtr<VoidCallback> = 0);
+    void requestPermission(PassOwnPtr<VoidCallback> = nullptr);
 
     virtual void stop() OVERRIDE;
 
@@ -77,15 +77,15 @@ private:
 
     class NotificationRequestCallback : public RefCounted<NotificationRequestCallback> {
     public:
-        static PassRefPtr<NotificationRequestCallback> createAndStartTimer(NotificationCenter*, PassRefPtr<VoidCallback>);
+        static PassRefPtr<NotificationRequestCallback> createAndStartTimer(NotificationCenter*, PassOwnPtr<VoidCallback>);
         void startTimer();
         void timerFired(Timer<NotificationRequestCallback>*);
     private:
-        NotificationRequestCallback(NotificationCenter*, PassRefPtr<VoidCallback>);
+        NotificationRequestCallback(NotificationCenter*, PassOwnPtr<VoidCallback>);
 
         RefPtr<NotificationCenter> m_notificationCenter;
         Timer<NotificationRequestCallback> m_timer;
-        RefPtr<VoidCallback> m_callback;
+        OwnPtr<VoidCallback> m_callback;
     };
 
     void requestTimedOut(NotificationRequestCallback*);