Expose Zones.

tests/lib/async/catch_errors_test.dart

 // Copyright (c) 2013, 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.
 
 import 'package:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'catch_errors.dart';
 
 main() {
   asyncStart();
-  // Make sure `catchErrors` shuts down the error stream when the synchronous
-  // operation is done and there isn't any asynchronous pending callback.
+
+  // Make sure `catchErrors` does not execute the error callback.
   catchErrors(() {
     return 'allDone';
-  }).listen((x) {
-      Expect.fail("Unexpected callback");
-    },
-    onDone: () {
-      asyncEnd();
-    });
+  }).listen((x) { Expect.fail("Unexpected callback"); });
+
+  // Wait one cycle before shutting down the test.
+  Timer.run(asyncEnd);
 }