Add a thread-safety assertion in DEFINE_STATIC_LOCAL

Source/wtf/Threading.h

Index: Source/wtf/Threading.h
diff --git a/Source/wtf/Threading.h b/Source/wtf/Threading.h
index e89dcb793295befc0b136be712fa72e6a6c9d766..be9833ccb42753c8d9d796600be36da97800cfd9 100644
--- a/Source/wtf/Threading.h
+++ b/Source/wtf/Threading.h
@@ -63,6 +63,12 @@ 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;