Complete support for Windows TLS destructors

runtime/vm/thread.h

Index: runtime/vm/thread.h
diff --git a/runtime/vm/thread.h b/runtime/vm/thread.h
index 49483e9e1dac2c89070c216eeebb03ee836cd616..5ab7f7d04ccc2785a7bdcfa6181573d664e540e8 100644
--- a/runtime/vm/thread.h
+++ b/runtime/vm/thread.h
@@ -144,11 +144,6 @@ class Thread {
   // TODO(koda): Always run GC in separate thread.
   static void PrepareForGC();
 
-#if defined(TARGET_OS_WINDOWS)
-  // Clears the state of the current thread and frees the allocation.
-  static void CleanUp();
-#endif
-
   // Called at VM startup.
   static void InitOnceBeforeIsolate();
   static void InitOnceAfterObjectAndStubCode();