Replace ReceivePorts with asyncStart|End in some tests.

tests/lib/async/catch_errors17_test.dart

Index: tests/lib/async/catch_errors17_test.dart
diff --git a/tests/lib/async/catch_errors17_test.dart b/tests/lib/async/catch_errors17_test.dart
index bf19b09b29c9f972c0003fc859b74d648c2048cd..8cb45c30e2100a130348e5904bc05778be5b8a74 100644
--- a/tests/lib/async/catch_errors17_test.dart
+++ b/tests/lib/async/catch_errors17_test.dart
@@ -2,15 +2,13 @@
 // 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 'dart:isolate';
 import 'catch_errors.dart';
 
 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();
+  asyncStart();
   var events = [];
   StreamController controller;
   // Test that errors do not cross zone boundaries.
@@ -40,6 +38,6 @@ main() {
                                  "inner done",
                                 ],
                                 events);
-              port.close();
+              asyncEnd();
             });
 }