Oilpan: make DOMWindowProperty a GC mixin.

Source/core/frame/History.cpp

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 30 matching lines @@
 #include "wtf/MainThread.h"
 
 namespace blink {
 
 History::History(LocalFrame* frame)
     : DOMWindowProperty(frame)
     , m_lastStateObjectRequested(nullptr)
 {
 }
 
+void History::trace(Visitor* visitor)
+{
+    DOMWindowProperty::trace(visitor);
+}
+
 unsigned History::length() const
 {
     if (!m_frame)
         return 0;
     if (!m_frame->page())
         return 0;
     return m_frame->page()->backForward().backForwardListCount();
 }
 
 SerializedScriptValue* History::state()
@@ skipping 69 matching lines @@
     KURL fullURL = urlForState(urlString);
     if (!fullURL.isValid() || !m_frame->document()->securityOrigin()->canRequest(fullURL)) {
         // We can safely expose the URL to JavaScript, as a) no redirection takes place: JavaScript already had this URL, b) JavaScript can only access a same-origin History object.
         exceptionState.throwSecurityError("A history state object with URL '" + fullURL.elidedString() + "' cannot be created in a document with origin '" + m_frame->document()->securityOrigin()->toString() + "'.");
         return;
     }
     m_frame->loader().updateForSameDocumentNavigation(fullURL, SameDocumentNavigationHistoryApi, data, type);
 }
 
 } // namespace blink