Oilpan: make DOMWindowProperty a GC mixin.

Source/modules/netinfo/NavigatorNetworkInformation.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/netinfo/NavigatorNetworkInformation.h"
 
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Navigator.h"
 #include "modules/netinfo/NetworkInformation.h"
 
 namespace blink {
 
 NavigatorNetworkInformation::NavigatorNetworkInformation(Navigator& navigator)
     : DOMWindowProperty(navigator.frame())
 {
 }
 
-NavigatorNetworkInformation::~NavigatorNetworkInformation()
-{
-}
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(NavigatorNetworkInformation);
 
 NavigatorNetworkInformation& NavigatorNetworkInformation::from(Navigator& navigator)
 {
     NavigatorNetworkInformation* supplement = toNavigatorNetworkInformation(navigator);
     if (!supplement) {
         supplement = new NavigatorNetworkInformation(navigator);
         provideTo(navigator, supplementName(), adoptPtrWillBeNoop(supplement));
     }
     return *supplement;
 }
@@ skipping 19 matching lines @@
         ASSERT(frame()->domWindow());
         m_connection = NetworkInformation::create(frame()->domWindow()->executionContext());
     }
     return m_connection.get();
 }
 
 void NavigatorNetworkInformation::trace(Visitor* visitor)
 {
     visitor->trace(m_connection);
     WillBeHeapSupplement<Navigator>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
 }
 
 } // namespace blink