Fix flaky message queue test.

runtime/vm/message_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 "platform/assert.h"
 #include "vm/message.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
@@ skipping 112 matching lines @@
     MonitorLocker ml(sync);
     ml.Notify();
   }
 
   // Wait for the other thread to fill the queue a bit.
   while (!peer.HasMessage()) {
     MonitorLocker ml(sync);
     ml.Wait(5);
   }
 
-  for (int i = 0; i < 3; i++) {
+  int i = 0;
+  while (i < 3) {
     Message* msg = queue->Dequeue(0);
-    EXPECT(msg != NULL);
-    EXPECT_EQ(i + 10, msg->dest_port());
-    EXPECT_EQ(i + 100, msg->reply_port());
-    EXPECT_EQ(i + 1000, *(reinterpret_cast<int*>(msg->data())));
-    delete msg;
+    // Dequeue(0) can return NULL due to spurious wakeup.
+    if (msg != NULL) {
+      EXPECT_EQ(i + 10, msg->dest_port());
+      EXPECT_EQ(i + 100, msg->reply_port());
+      EXPECT_EQ(i + 1000, *(reinterpret_cast<int*>(msg->data())));
+      delete msg;
+      i++;
+    }
   }
-  for (int i = 0; i < 3; i++) {
+
+  i = 0;
+  while (i < 3) {
     Message* msg = queue->Dequeue(0);
-    EXPECT(msg != NULL);
-    EXPECT_EQ(i + 20, msg->dest_port());
-    EXPECT_EQ(i + 200, msg->reply_port());
-    EXPECT_EQ(i + 2000, *(reinterpret_cast<int*>(msg->data())));
-    delete msg;
+    // Dequeue(0) can return NULL due to spurious wakeup.
+    if (msg != NULL) {
+      EXPECT_EQ(i + 20, msg->dest_port());
+      EXPECT_EQ(i + 200, msg->reply_port());
+      EXPECT_EQ(i + 2000, *(reinterpret_cast<int*>(msg->data())));
+      delete msg;
+      i++;
+    }
   }
   shared_queue = NULL;
   delete queue;
   Dart::ShutdownIsolate();
 }
 
 
 TEST_CASE(MessageQueue_WaitNotify) {
   sync = new Monitor();
 
@@ skipping 122 matching lines @@
   Dart_Port port1 = 1;
 
   EXPECT(!queue_peer.HasMessage());
   queue.Flush(port1);
 
   // Queue is still empty.
   EXPECT(!queue_peer.HasMessage());
 }
 
 }  // namespace dart