Revert https://code.google.com/p/dart/source/detail?r=597

vm/message_queue.cc

 // Copyright (c) 2011, 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 "vm/message_queue.h"
 
 namespace dart {
 
 MessageQueue::~MessageQueue() {
   // Ensure that all pending messages have been released.
@@ skipping 22 matching lines @@
     tail_ = msg;
   }
 
   monitor_.Exit();
 }
 
 
 PortMessage* MessageQueue::Dequeue(int64_t millis) {
   MonitorLocker ml(&monitor_);
   PortMessage* result = head_;
-  // Wait may wake up prematurely, so we need to loop until result != NULL
-  while (result == NULL) {
+  if (result == NULL) {
     ml.Wait(millis);
     result = head_;
-    // If there's a time-out the caller must check for NULL anyway.
-    if (0 < millis)
-      break;
   }
   if (result != NULL) {
     head_ = result->next_;
     // The following update to tail_ is not strictly needed.
     if (head_ == NULL) {
       tail_ = NULL;
     }
 #if DEBUG
     result->next_ = result;  // Make sure to trigger ASSERT in Enqueue.
 #endif  // DEBUG
@@ skipping 34 matching lines @@
   tail_ = NULL;
   while (cur != NULL) {
     PortMessage* next = cur->next_;
     delete cur;
     cur = next;
   }
 }
 
 
 }  // namespace dart