Avoid leaking ThreadingPrimitives.h from StackStats.h when collection is off.

Source/wtf/WTFThreadData.h

 /*
  * Copyright (C) 2008 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 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 #ifndef WTFThreadData_h
 #define WTFThreadData_h
 
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/Noncopyable.h"
-#include "wtf/StackStats.h"
 #include "wtf/ThreadSpecific.h"
 #include "wtf/Threading.h"
 #include "wtf/WTFExport.h"
 #include "wtf/text/StringHash.h"
 
 namespace WTF {
 
 class AtomicStringTable;
 struct ICUConverterWrapper;
 
@@ skipping 36 matching lines @@
         WTFThreadData::staticData = new ThreadSpecific<WTFThreadData>;
     return **WTFThreadData::staticData;
 }
 
 } // namespace WTF
 
 using WTF::WTFThreadData;
 using WTF::wtfThreadData;
 
 #endif // WTFThreadData_h