Rename Thread -> OSThread.

runtime/vm/os_thread_win.h

 // Copyright (c) 2012, 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_WIN_H_
-#define VM_THREAD_WIN_H_
+#ifndef VM_OS_THREAD_WIN_H_
+#define VM_OS_THREAD_WIN_H_
 
-#if !defined(VM_THREAD_H_)
-#error Do not include thread_win.h directly; use thread.h instead.
+#if !defined(VM_OS_THREAD_H_)
+#error Do not include os_thread_win.h directly; use os_thread.h instead.
 #endif
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 
 namespace dart {
 
 typedef DWORD ThreadLocalKey;
 typedef DWORD ThreadId;
 
@@ skipping 91 matching lines @@
   friend class Monitor;
   friend class OS;
   friend unsigned int __stdcall ThreadEntry(void* data_ptr);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(MonitorData);
 };
 
 }  // namespace dart
 
-#endif  // VM_THREAD_WIN_H_
+#endif  // VM_OS_THREAD_WIN_H_