Temporary fix to mac buildbot issue. We need to figure out why

tools/test.dart

 #!/usr/bin/env dart
 // 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.
 
 /**
  * This file is the entrypoint of the dart test suite.  This suite is used
  * to test:
  *
  *     1. the dart vm
@@ skipping 109 matching lines @@
       if (selectors.containsKey(name)) {
         queue.addTestSuite(
             new StandardTestSuite.forDirectory(conf, testSuiteDir));
       }
     }
   }
 
   // Start global http server that serves the entire dart repo.
   // The http server is available on localhost:9876 for any
   // test that needs to load resources from the repo over http.
-  if (!listTests) startHttpServer('127.0.0.1', 9876);
-
-  // Start process queue.
-  new ProcessQueue(
-      maxProcesses,
-      progressIndicator,
-      startTime,
-      printTiming,
-      enqueueConfiguration,
-      () {
-        if (!listTests) terminateHttpServer();
-      },
-      verbose,
-      listTests);
+  //
+  // TODO(ager): Simplify when mac os startHttpServer issues has
+  // been resolved.
+  if (!listTests) {
+    startHttpServer('127.0.0.1', 9876).then((_) {
+      // Start process queue.
+      new ProcessQueue(maxProcesses,
+                       progressIndicator,
+                       startTime,
+                       printTiming,
+                       enqueueConfiguration,
+                       () {
+                         if (!listTests) terminateHttpServer();
+                       },
+                       verbose,
+                       listTests);
+    });
+  } else {
+    // Start process queue.
+    new ProcessQueue(maxProcesses,
+                     progressIndicator,
+                     startTime,
+                     printTiming,
+                     enqueueConfiguration,
+                     () => null,
+                     verbose,
+                     listTests);
+  }
 }