Revert of Oilpan: fix build after r180052. (https://codereview.chromium.org/460983002/)

Reason for revert:
Android Builder failed to compile

Original issue's description:
> Oilpan: fix build after r180052.
> 
> TBR=haraken,oilpan-reviews
> BUG=383813
> NOTRY=true
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180061

TBR=haraken@chromium.org,oilpan-reviews@chromium.org,sigbjornf@opera.com
NOTREECHECKS=true
NOTRY=true
BUG=383813

Review URL: https://codereview.chromium.org/461963002

git-svn-id: svn://svn.chromium.org/blink/trunk@180062 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/dom/FullscreenElementStack.h

@@ -36,7 +36,6 @@
 #include "platform/geometry/LayoutRect.h"
 #include "wtf/Deque.h"
 #include "wtf/RefPtr.h"
-#include "wtf/TypeTraits.h"
 #include "wtf/Vector.h"
 
 namespace blink {
@@ -141,9 +140,4 @@ inline FullscreenElementStack* FullscreenElementStack::fromIfExists(Document& do
 
 } // namespace blink
 
-// Needed by the HeapVector<> element stack.
-template<>struct WTF::IsPod<blink::FullscreenElementStack::RequestType> {
-    static const bool value = true;
-};
-
 #endif // FullscreenElementStack_h