Pass implementation object to supplemental classes by reference

Source/modules/serviceworkers/NavigatorServiceWorker.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NavigatorServiceWorker_h
 #define NavigatorServiceWorker_h
 
 #include "bindings/v8/ScriptPromise.h"
 #include "core/frame/Navigator.h"
 #include "platform/Supplementable.h"
 
 namespace WebCore {
 
 class Navigator;
 class ServiceWorkerContainer;
 
 class NavigatorServiceWorker FINAL : public Supplement<Navigator>, DOMWindowProperty {
 public:
     virtual ~NavigatorServiceWorker();
-    static NavigatorServiceWorker* from(Navigator*);
-    static NavigatorServiceWorker* toNavigatorServiceWorker(Navigator* navigator) { return static_cast<NavigatorServiceWorker*>(Supplement<Navigator>::from(navigator, supplementName())); }
+    static NavigatorServiceWorker& from(Navigator&);
+    static NavigatorServiceWorker* toNavigatorServiceWorker(Navigator& navigator) { return static_cast<NavigatorServiceWorker*>(Supplement<Navigator>::from(navigator, supplementName())); }
     static const char* supplementName();
 
-    static ServiceWorkerContainer* serviceWorker(Navigator*);
+    static ServiceWorkerContainer* serviceWorker(Navigator&);
 
 private:
-    explicit NavigatorServiceWorker(Navigator*);
+    explicit NavigatorServiceWorker(Navigator&);
     ServiceWorkerContainer* serviceWorker();
 
     RefPtr<ServiceWorkerContainer> m_serviceWorker;
 };
 
 } // namespace WebCore
 
 #endif // NavigatorServiceWorker_h