catchErrors and waitForCompletion now based on runZonedExperimental.

tests/lib/async/run_zoned2_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:expect/expect.dart";
 import 'dart:async';
 import 'dart:isolate';
 
 main() {
   // We keep a ReceivePort open until all tests are done. This way the VM will
   // hang if the callbacks are not invoked and the test will time out.
   var port = new ReceivePort();
-  // Make sure `catchErrors` shuts down the error stream when the synchronous
-  // operation is done and there isn't any asynchronous pending callback.
-  catchErrors(() {
-    return 'allDone';
-  }).listen((x) {
-      Expect.fail("Unexpected callback");
-    },
-    onDone: () {
-      port.close();
-    });
+  // Ensure that `runZoned` is done when a synchronous call finishes.
+  runZonedExperimental(() => 499,
+                       onDone: port.close);
 }