Implement monitors.

Change-Id: Ifc7a801f9cbcdfbc1e1af5c905261dfadaa60f45
diff --git a/src/thread_list.h b/src/thread_list.h
index 5630b29..aa1415a 100644
--- a/src/thread_list.h
+++ b/src/thread_list.h
@@ -59,12 +59,12 @@
   std::bitset<kMaxThreadId> allocated_ids_;
   std::list<Thread*> list_;
 
-  pthread_cond_t thread_start_cond_;
+  ConditionVariable thread_start_cond_;
 
   // This lock guards every thread's suspend_count_ field...
   mutable Mutex thread_suspend_count_lock_;
   // ...and is used in conjunction with this condition variable.
-  pthread_cond_t thread_suspend_count_cond_;
+  ConditionVariable thread_suspend_count_cond_;
 
   friend class Thread;
   friend class ThreadListLock;