VM: Small clean up and const-ness fix for Thread/OSThread constants.

runtime/bin/thread_macos.cc

 // 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.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "bin/thread.h"
 
 #include <sys/errno.h>  // NOLINT
@@ skipping 89 matching lines @@
   result = pthread_create(&tid, &attr, ThreadStart, data);
   RETURN_ON_PTHREAD_FAILURE(result);
 
   result = pthread_attr_destroy(&attr);
   RETURN_ON_PTHREAD_FAILURE(result);
 
   return 0;
 }
 
 
-ThreadLocalKey Thread::kUnsetThreadLocalKey = static_cast<pthread_key_t>(-1);
-ThreadId Thread::kInvalidThreadId = reinterpret_cast<ThreadId>(NULL);
+const ThreadLocalKey Thread::kUnsetThreadLocalKey =
+    static_cast<pthread_key_t>(-1);
+const ThreadId Thread::kInvalidThreadId = reinterpret_cast<ThreadId>(NULL);
 
 ThreadLocalKey Thread::CreateThreadLocal() {
   pthread_key_t key = kUnsetThreadLocalKey;
   int result = pthread_key_create(&key, NULL);
   VALIDATE_PTHREAD_RESULT(result);
   ASSERT(key != kUnsetThreadLocalKey);
   return key;
 }
 
 
@@ skipping 212 matching lines @@
 void Monitor::NotifyAll() {
   // TODO(iposva): Do we need to track lock owners?
   int result = pthread_cond_broadcast(data_.cond());
   VALIDATE_PTHREAD_RESULT(result);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)