Add MutexLocker and MonitorLocker to platform/bin

runtime/bin/thread_pool.cc

Index: runtime/bin/thread_pool.cc
diff --git a/runtime/bin/thread_pool.cc b/runtime/bin/thread_pool.cc
index d93b8f844aa24e5423a2d55032ac1216e9354925..36960a72303b798454eb01b72b3cfa802a1044ce 100644
--- a/runtime/bin/thread_pool.cc
+++ b/runtime/bin/thread_pool.cc
@@ -4,47 +4,45 @@
 
 #include "bin/thread_pool.h"
 
+#include "bin/thread.h"
+
 void TaskQueue::Insert(TaskQueueEntry* entry) {
+  MonitorLocker monitor(&monitor_);
   monitor_.Enter();
   if (head_ == NULL) {
     head_ = entry;
     tail_ = entry;
-    monitor_.Notify();
+    monitor.Notify();
   } else {
     tail_->set_next(entry);
     tail_ = entry;
   }
-  monitor_.Exit();
 }
 
 
 TaskQueueEntry* TaskQueue::Remove() {
-  monitor_.Enter();
+  MonitorLocker monitor(&monitor_);
   TaskQueueEntry* result = head_;
   while (result == NULL) {
     if (terminate_) {
-      monitor_.Exit();
       return NULL;
     }
-    monitor_.Wait(dart::Monitor::kNoTimeout);
+    monitor.Wait();
     if (terminate_) {
-      monitor_.Exit();
       return NULL;
     }
     result = head_;
   }
   head_ = result->next();
   ASSERT(head_ != NULL || tail_ == result);
-  monitor_.Exit();
   return result;
 }
 
 
 void TaskQueue::Shutdown() {
-  monitor_.Enter();
+  MonitorLocker monitor(&monitor_);
   terminate_ = true;
-  monitor_.NotifyAll();
-  monitor_.Exit();
+  monitor.NotifyAll();
 }