Use platform implementation of Monitor in thread pool

runtime/bin/thread_pool_macos.h

Index: runtime/bin/thread_pool_macos.h
diff --git a/runtime/bin/thread_pool_macos.h b/runtime/bin/thread_pool_macos.h
index 8fe7d047342f0bcd4d24e8c32cea166002030197..d29b6f8b1dcdb4640c19f8739ca8e93a86b065ec 100644
--- a/runtime/bin/thread_pool_macos.h
+++ b/runtime/bin/thread_pool_macos.h
@@ -10,24 +10,6 @@
 #include "platform/globals.h"
 
 
-class TaskQueueData {
- private:
-  TaskQueueData() {}
-  ~TaskQueueData() {}
-
-  pthread_mutex_t* mutex() { return &mutex_; }
-  pthread_cond_t* cond() { return &cond_; }
-
-  pthread_mutex_t mutex_;
-  pthread_cond_t cond_;
-
-  friend class TaskQueue;
-
-  DISALLOW_ALLOCATION();
-  DISALLOW_COPY_AND_ASSIGN(TaskQueueData);
-};
-
-
 class ThreadPoolData {
  private:
   ThreadPoolData() {}