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 18 matching lines @@
 #define FullscreenElementStack_h
 
 #include "core/dom/Document.h"
 #include "core/dom/DocumentLifecycleObserver.h"
 #include "core/dom/Element.h"
 #include "platform/Supplementable.h"
 #include "platform/Timer.h"
 #include "platform/geometry/LayoutRect.h"
 #include "wtf/Deque.h"
 #include "wtf/RefPtr.h"
+#include "wtf/TypeTraits.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class RenderFullScreen;
 class RenderStyle;
 
 class FullscreenElementStack FINAL
     : public NoBaseWillBeGarbageCollectedFinalized<FullscreenElementStack>
     , public DocumentSupplement
@@ skipping 84 matching lines @@
 
 inline FullscreenElementStack* FullscreenElementStack::fromIfExists(Document& document)
 {
     if (!document.hasFullscreenElementStack())
         return 0;
     return fromIfExistsSlow(document);
 }
 
 } // namespace blink
 
+// Needed by the HeapVector<> element stack.
+template<>struct WTF::IsPod<blink::FullscreenElementStack::RequestType> {
+    static const bool value = true;
+};
+
 #endif // FullscreenElementStack_h