Uses an open thread handle as the ThreadJoinId on Windows.

runtime/vm/os_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"  // NOLINT
 #if defined(TARGET_OS_MACOS)
 
 #include "vm/os_thread.h"
 
 #include <sys/errno.h>  // NOLINT
@@ skipping 150 matching lines @@
 ThreadId OSThread::GetCurrentThreadId() {
   return pthread_self();
 }
 
 
 ThreadId OSThread::GetCurrentThreadTraceId() {
   return ThreadIdFromIntPtr(pthread_mach_thread_np(pthread_self()));
 }
 
 
-ThreadJoinId OSThread::GetCurrentThreadJoinId() {
-  return pthread_self();
+ThreadJoinId OSThread::GetCurrentThreadJoinId(OSThread* thread) {
+  ASSERT(thread != NULL);
+  // Make sure we're filling in the join id for the current thread.
+  ASSERT(thread->id() == GetCurrentThreadId());
+  // Make sure the join_id_ hasn't been set, yet.
+  DEBUG_ASSERT(thread->join_id_ == kInvalidThreadJoinId);
+  pthread_t id = pthread_self();
+#if defined(DEBUG)
+  thread->join_id_ = id;
+#endif
+  return id;
 }
 
 
 void OSThread::Join(ThreadJoinId id) {
   int result = pthread_join(id, NULL);
   ASSERT(result == 0);
 }
 
 
 intptr_t OSThread::ThreadIdToIntPtr(ThreadId id) {
@@ skipping 227 matching lines @@
 void Monitor::NotifyAll() {
   // When running with assertions enabled we track the owner.
   ASSERT(IsOwnedByCurrentThread());
   int result = pthread_cond_broadcast(data_.cond());
   VALIDATE_PTHREAD_RESULT(result);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)