Call known TLS destructors on Windows

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index 46da230d3bc0af3224ecb1914e4b491c50a80c81..069d2d51c349a212b2e868ba3c56199dd97851e0 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -537,5 +537,15 @@ Thread* ThreadIterator::Next() {
   return current;
 }
 
+#if defined(TARGET_OS_WINDOWS)
+// This function is invoked by |OnThreadExit| found in os_thread_win.cc.
+void ThreadCleanupOnExit() {
+  // Windows does not support TLS destructors (see os_thread_win.cc for
+  // context). As a work around, we maintain a list of functions to be
+  // executed when a thread exits in |OnThreadExit| in os_thread_win.cc.
+  Thread::CleanUp();
+}
+#endif
+
 
 }  // namespace dart