Call known TLS destructors on Windows

runtime/vm/thread.h

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_THREAD_H_
 #define VM_THREAD_H_
 
 #include "vm/globals.h"
 #include "vm/handles.h"
 #include "vm/os_thread.h"
@@ skipping 494 matching lines @@
   // Returns false when there are no more threads left.
   bool HasNext() const;
 
   // Returns the current thread and moves forward.
   Thread* Next();
 
  private:
   Thread* next_;
 };
 
+#if defined(TARGET_OS_WINDOWS)
+// Clears the state of the current thread and frees the allocation.
+void WindowsThreadCleanUp();
+#endif

[siva, 2015/10/13 21:30:54]

Not sure why this needs to be here in this common file as opposed to
os_thread_win.h

Same comment for Thread::Cleanup it is not needed here can be done entirely in
os_thread_win.cc

[Cutch, 2015/10/14 14:43:18]

This is structured like this because the Thread::Cleanup code needs the Thread
class and its destructor. This isn't available in os_thread_win.*

I've added lots of comments.

+
 }  // namespace dart
 
 #endif  // VM_THREAD_H_