Oilpan: fix build after r180052.

Source/core/dom/FullscreenElementStack.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 122 matching lines @@
 
 inline FullscreenElementStack* FullscreenElementStack::fromIfExists(Document& document)
 {
     if (!document.hasFullscreenElementStack())
         return 0;
     return fromIfExistsSlow(document);
 }
 
 } // namespace blink
 
+// Needed by the HeapVector<> element stack.
+namespace WTF {
+
+template<>struct IsPod<blink::FullscreenElementStack::RequestType> {
+    static const bool value = true;
+};
+
+} // namespace WTF
+
 #endif // FullscreenElementStack_h