Add a thread-safety assertion in DEFINE_STATIC_LOCAL

Source/wtf/ThreadingWin.cpp

Index: Source/wtf/ThreadingWin.cpp
diff --git a/Source/wtf/ThreadingWin.cpp b/Source/wtf/ThreadingWin.cpp
index cc342571014f09a02c1ea9d3a519d4a42200e44c..06cd6b0f2b7e902cfb1026b1b6086b895a6a69a6 100644
--- a/Source/wtf/ThreadingWin.cpp
+++ b/Source/wtf/ThreadingWin.cpp
@@ -391,6 +391,33 @@ DWORD absoluteTimeToWaitTimeoutInterval(double absoluteTime)
     return static_cast<DWORD>((absoluteTime - currentTime) * 1000.0);
 }
 
+#if ENABLE(ASSERT)
+static bool s_threadCreated = false;
+
+struct ThreadCreationRecorder {
+    ThreadCreationRecorder()
+    {
+        ASSERT(!s_threadCreated);
+        s_threadCreated = true;
+    }
+};
+
+bool isAtomicallyInitializedStaticMutexLockHeld()
+{
+    return atomicallyInitializedStaticMutex && atomicallyInitializedStaticMutex->locked();
+}
+
+bool isBeforeThreadCreated()
+{
+    return !s_threadCreated;
+}
+
+void willCreateThread()
+{
+    static ThreadCreationRecorder recorder;
+}
+#endif
+
 } // namespace WTF
 
 #endif // OS(WIN)