Use platform implementation of Monitor in thread pool

runtime/bin/thread_pool.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 "bin/thread_pool.h"
 
+void TaskQueue::Insert(TaskQueueEntry* entry) {
+  monitor_.Enter();
+  if (head_ == NULL) {
+    head_ = entry;
+    tail_ = entry;
+    monitor_.Notify();
+  } else {
+    tail_->set_next(entry);
+    tail_ = entry;
+  }
+  monitor_.Exit();
+}
+
+
+TaskQueueEntry* TaskQueue::Remove() {
+  monitor_.Enter();
+  TaskQueueEntry* result = head_;
+  while (result == NULL) {
+    if (terminate_) {
+      monitor_.Exit();
+      return NULL;
+    }
+    monitor_.Wait(dart::Monitor::kNoTimeout);
+    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();
+  terminate_ = true;
+  monitor_.NotifyAll();
+  monitor_.Exit();
+}
+
+
 void ThreadPool::InsertTask(Task task) {
   TaskQueueEntry* entry = new TaskQueueEntry(task);
   queue_.Insert(entry);
 }
 
 
 Task ThreadPool::WaitForTask() {
   TaskQueueEntry* entry = queue_.Remove();
   if (entry == NULL) {
     return NULL;
@@ skipping 12 matching lines @@
   while (!pool->terminate_) {
     if (Dart_IsVMFlagSet("trace_thread_pool")) {
       printf("Waiting for task\n");
     }
     Task task = pool->WaitForTask();
     if (pool->terminate_) return NULL;
     (*(pool->task_handler_))(task);
   }
   return NULL;
 };