Fix MacOS build

runtime/vm/os_thread_linux.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_LINUX)
 
 #include "vm/os_thread.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 152 matching lines @@
   return false;
 }
 
 
 intptr_t OSThread::ThreadIdToIntPtr(ThreadId id) {
   ASSERT(sizeof(id) == sizeof(intptr_t));
   return static_cast<intptr_t>(id);
 }
 
 
+ThreadId OSThread::ThreadIdFromIntPtr(intptr_t id) {
+  return static_cast<ThreadId>(id);
+}
+
+
 bool OSThread::Compare(ThreadId a, ThreadId b) {
   return pthread_equal(a, b) != 0;
 }
 
 
 void OSThread::GetThreadCpuUsage(ThreadId thread_id, int64_t* cpu_usage) {
   ASSERT(thread_id == GetCurrentThreadId());
   ASSERT(cpu_usage != NULL);
   struct timespec ts;
   int r = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
@@ skipping 167 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 dart
 
 #endif  // defined(TARGET_OS_LINUX)