Handle spurious wakeups properly.

runtime/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 20 matching lines @@
     // Append at the tail.
     tail_->next_ = msg;
     tail_ = msg;
   }
 
   monitor_.Exit();
 }
 
 
 PortMessage* MessageQueue::Dequeue(int64_t millis) {
+  ASSERT(millis >= 0);
   MonitorLocker ml(&monitor_);
   PortMessage* result = head_;
   if (result == NULL) {
     ml.Wait(millis);
     result = head_;
   }
   if (result != NULL) {
     head_ = result->next_;
     // The following update to tail_ is not strictly needed.
     if (head_ == NULL) {
@@ skipping 39 matching lines @@
   tail_ = NULL;
   while (cur != NULL) {
     PortMessage* next = cur->next_;
     delete cur;
     cur = next;
   }
 }
 
 
 }  // namespace dart