Oilpan: make DOMWindowProperty a GC mixin.

Source/modules/serviceworkers/NavigatorServiceWorker.cpp

 // 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.
 
 #include "config.h"
 #include "modules/serviceworkers/NavigatorServiceWorker.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Navigator.h"
 #include "modules/serviceworkers/ServiceWorkerContainer.h"
 
 namespace blink {
 
 NavigatorServiceWorker::NavigatorServiceWorker(Navigator& navigator)
     : DOMWindowProperty(navigator.frame())
 {
 }
 
-NavigatorServiceWorker::~NavigatorServiceWorker()
-{
-}
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(NavigatorServiceWorker);
 
 NavigatorServiceWorker* NavigatorServiceWorker::from(Document& document)
 {
     if (!document.frame() || !document.frame()->domWindow())
         return 0;
     Navigator& navigator = document.frame()->domWindow()->navigator();
     return &from(navigator);
 }
 
 NavigatorServiceWorker& NavigatorServiceWorker::from(Navigator& navigator)
@@ skipping 37 matching lines @@
     if (m_serviceWorker) {
         m_serviceWorker->willBeDetachedFromFrame();
         m_serviceWorker = nullptr;
     }
 }
 
 void NavigatorServiceWorker::trace(Visitor* visitor)
 {
     visitor->trace(m_serviceWorker);
     WillBeHeapSupplement<Navigator>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
 }
 
 } // namespace blink