Call known TLS destructors on Windows

runtime/vm/thread.h

Index: runtime/vm/thread.h
diff --git a/runtime/vm/thread.h b/runtime/vm/thread.h
index a27e6730bcece9856c492c647a6acdaf7d49b6bd..1786070a3bf145f3a5f25f716ccb2040e749af1a 100644
--- a/runtime/vm/thread.h
+++ b/runtime/vm/thread.h
@@ -512,6 +512,11 @@ class ThreadIterator : public ValueObject {
   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_