Fix deadlock that can occur while handling service messages at a breakpoint.

runtime/vm/message_handler_test.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 "vm/message_handler.h"
 #include "vm/port.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
@@ skipping 130 matching lines @@
   // The notify callback is called.
   EXPECT_EQ(2, handler.notify_count());
 
   // The message has been added to the correct queue.
   EXPECT(message == handler_peer.oob_queue()->Dequeue());
   EXPECT(NULL == handler_peer.queue()->Dequeue());
   delete message;
 }
 
 
+UNIT_TEST_CASE(MessageHandler_HasOOBMessages) {
+  TestMessageHandler handler;
+  MessageHandlerTestPeer handler_peer(&handler);
+
+  EXPECT(!handler.HasOOBMessages());
+
+  // Post a normal message.
+  Message* message = new Message(1, NULL, 0, Message::kNormalPriority);
+  handler_peer.PostMessage(message);
+  EXPECT(!handler.HasOOBMessages());
+
+  // Post an oob message.
+  message = new Message(1, NULL, 0, Message::kOOBPriority);
+  handler_peer.PostMessage(message);
+  EXPECT(handler.HasOOBMessages());
+
+  // Delete all pending messages.
+  handler_peer.CloseAllPorts();
+}
+
+
 UNIT_TEST_CASE(MessageHandler_ClosePort) {
   TestMessageHandler handler;
   MessageHandlerTestPeer handler_peer(&handler);
   Message* message1 = new Message(1, NULL, 0, Message::kNormalPriority);
   handler_peer.PostMessage(message1);
   Message* message2 = new Message(2, NULL, 0, Message::kNormalPriority);
   handler_peer.PostMessage(message2);
 
   handler_peer.ClosePort(1);
 
@@ skipping 141 matching lines @@
   EXPECT_EQ(port, handler_ports[0]);
   for (int i = 1; i < 11; i++) {
     EXPECT_EQ(ports[i - 1], handler_ports[i]);
   }
   handler_peer.decrement_live_ports();
   EXPECT(!handler.HasLivePorts());
   PortMap::ClosePorts(&handler);
 }
 
 }  // namespace dart