Pass implementation object to supplemental classes by reference

Source/modules/notifications/DOMWindowNotifications.h

Index: Source/modules/notifications/DOMWindowNotifications.h
diff --git a/Source/modules/notifications/DOMWindowNotifications.h b/Source/modules/notifications/DOMWindowNotifications.h
index 255a792386e0a369f5d714acbad2a7cfff3dc20a..f9a19f23ed33321050338420f6cfdefa5f65e609 100644
--- a/Source/modules/notifications/DOMWindowNotifications.h
+++ b/Source/modules/notifications/DOMWindowNotifications.h
@@ -43,19 +43,19 @@ class DOMWindowNotifications FINAL : public Supplement<DOMWindow>, public DOMWin
 public:
     virtual ~DOMWindowNotifications();
 
-    static NotificationCenter* webkitNotifications(DOMWindow*);
-    static DOMWindowNotifications* from(DOMWindow*);
+    static NotificationCenter* webkitNotifications(DOMWindow&);
+    static DOMWindowNotifications& from(DOMWindow&);
 
     virtual void willDestroyGlobalObjectInFrame() OVERRIDE;
     virtual void willDetachGlobalObjectFromFrame() OVERRIDE;
 
 private:
-    explicit DOMWindowNotifications(DOMWindow*);
+    explicit DOMWindowNotifications(DOMWindow&);
 
     NotificationCenter* webkitNotifications();
     static const char* supplementName();
 
-    DOMWindow* m_window;
+    DOMWindow& m_window;
     RefPtrWillBePersistent<NotificationCenter> m_notificationCenter;
 };