Add a thread-safety assertion in DEFINE_STATIC_LOCAL

Source/wtf/Threading.h

 /*
  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
  *
  * 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.
@@ skipping 58 matching lines @@
 typedef uint32_t ThreadIdentifier;
 #else
 typedef intptr_t ThreadIdentifier;
 #endif
 
 WTF_EXPORT ThreadIdentifier currentThread();
 
 WTF_EXPORT void lockAtomicallyInitializedStaticMutex();
 WTF_EXPORT void unlockAtomicallyInitializedStaticMutex();
 
+#if ENABLE(ASSERT)
+WTF_EXPORT bool isAtomicallyInitializedStaticMutexLockHeld();
+WTF_EXPORT bool isBeforeThreadCreated();
+WTF_EXPORT void willCreateThread();
+#endif
+
 } // namespace WTF
 
 using WTF::ThreadIdentifier;
 using WTF::currentThread;
 
 #endif // Threading_h