Revert my last change. Odd test failures that I will investigate tomorrow.

runtime/vm/message.h

 // 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.
 
 #ifndef VM_MESSAGE_H_
 #define VM_MESSAGE_H_
 
 #include "vm/thread.h"
 
 // Duplicated from dart_api.h to avoid including the whole header.
@@ skipping 49 matching lines @@
 };
 
 // There is a message queue per isolate.
 class MessageQueue {
  public:
   MessageQueue();
   ~MessageQueue();
 
   void Enqueue(Message* msg);
 
-  // Gets the next message from the message queue if available.
-  // Returns NULL if no message is available.
-  Message* Dequeue();
+  // Gets the next message from the message queue, possibly blocking
+  // if no message is available. 'millis' is a timeout in
+  // milliseconds. If 'millis' is 0, then this means to block
+  // indefinitely. May block if no message is available. May return
+  // NULL even if 'millis' is 0 due to spurious wakeups.
+  Message* Dequeue(int64_t millis);
+
+  // Gets the next message from the message queue if available.  Will
+  // not block.
+  Message* DequeueNoWait();
 
   void Flush(Dart_Port port);
   void FlushAll();
 
  private:
   friend class MessageQueueTestPeer;
 
+  Message* DequeueNoWaitHoldsLock();
+
+  Monitor monitor_;
   Message* head_[Message::kNumPriorities];
   Message* tail_[Message::kNumPriorities];
 
   DISALLOW_COPY_AND_ASSIGN(MessageQueue);
 };
 
 // A MessageHandler is an entity capable of accepting messages.
 class MessageHandler {
  protected:
+  MessageHandler();
+
   // Allows subclasses to provide custom message notification.
   virtual void MessageNotify(Message::Priority priority);
 
  public:
-  MessageHandler();
   virtual ~MessageHandler();
 
   // Allow subclasses to provide a handler name.
   virtual const char* name() const;
 
 #if defined(DEBUG)
   // Check that it is safe to access this message handler.
   //
   // For example, if this MessageHandler is an isolate, then it is
   // only safe to access it when the MessageHandler is the current
   // isolate.
   virtual void CheckAccess();
 #endif
 
   void PostMessage(Message* message);
   void ClosePort(Dart_Port port);
   void CloseAllPorts();
 
-  // Gets the next message from the message queue, possibly blocking
-  // if no message is available. 'millis' is a timeout in
-  // milliseconds. If 'millis' is 0, then this means to block
-  // indefinitely. May block if no message is available. May return
-  // NULL even if 'millis' is 0 due to spurious wakeups.
-  Message* Dequeue(int64_t millis);
-
-  // Gets the next message from the message queue if available.  Will
-  // not block.
-  Message* DequeueNoWait();
-
   // A message handler tracks how many live ports it has.
   bool HasLivePorts() const { return live_ports_ > 0; }
   void increment_live_ports() {
 #if defined(DEBUG)
     CheckAccess();
 #endif
     live_ports_++;
   }
   void decrement_live_ports() {
 #if defined(DEBUG)
     CheckAccess();
 #endif
     live_ports_--;
   }
 
   // Returns true if the handler is owned by the PortMap.
   //
   // This is used to delete handlers when their last live port is closed.
   virtual bool OwnedByPortMap() const { return false; }
 
+  MessageQueue* queue() const { return queue_; }
+
  private:
-  friend class MessageHandlerTestPeer;
-
-  Monitor monitor_;
   intptr_t live_ports_;
   MessageQueue* queue_;
 };
 
 }  // namespace dart
 
 #endif  // VM_MESSAGE_H_