Oilpan: make DOMWindowProperty a GC mixin.

Source/modules/credentialmanager/NavigatorCredentials.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/credentialmanager/NavigatorCredentials.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Navigator.h"
 #include "modules/credentialmanager/CredentialsContainer.h"
 
 namespace blink {
 
 NavigatorCredentials::NavigatorCredentials(Navigator& navigator)
     : DOMWindowProperty(navigator.frame())
 {
 }
 
-NavigatorCredentials::~NavigatorCredentials()
-{
-}
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(NavigatorCredentials);
 
 NavigatorCredentials& NavigatorCredentials::from(Navigator& navigator)
 {
     NavigatorCredentials* supplement = static_cast<NavigatorCredentials*>(WillBeHeapSupplement<Navigator>::from(navigator, supplementName()));
     if (!supplement) {
         supplement = new NavigatorCredentials(navigator);
         provideTo(navigator, supplementName(), adoptPtrWillBeNoop(supplement));
     }
     return *supplement;
 }
@@ skipping 12 matching lines @@
 {
     if (!m_credentialsContainer && frame())
         m_credentialsContainer = CredentialsContainer::create();
     return m_credentialsContainer.get();
 }
 
 void NavigatorCredentials::trace(Visitor* visitor)
 {
     visitor->trace(m_credentialsContainer);
     WillBeHeapSupplement<Navigator>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
 }
 
 } // namespace blink