Migrated test block 168 to Dart 2.0.

tests/lib/async/future_delayed_error_test.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.
-
-library future_delayed_error_test;
-
-import 'package:async_helper/async_helper.dart';
-import "package:expect/expect.dart";
-import 'dart:async';
-
-testImmediateError() {
-  asyncStart();
-  var future = new Future.error("error");
-  future.catchError((error) {
-    Expect.equals(error, "error");
-    asyncEnd();
-  });
-}
-
-Future get completedFuture {
-  var completer = new Completer();
-  completer.completeError("foobar");
-  return completer.future;
-}
-
-testDelayedError() {
-  asyncStart();
-  completedFuture.catchError((error) {
-    Expect.equals(error, "foobar");
-    asyncEnd();
-  });
-}
-
-main() {
-  testImmediateError();
-  testDelayedError();
-}