Fix tests for VM in checked mode.

pkg/http/test/request_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 request_test;
 
 import 'dart:io';
 
 import 'package:unittest/unittest.dart';
 import 'package:http/http.dart' as http;
@@ skipping 197 matching lines @@
 
   test('#maxRedirects', () {
     print("This test is known to be flaky, please ignore "
           "(debug prints below added by sgjesse@)");
     print("#maxRedirects test starting server...");
     startServer();
     print("#maxRedirects test server running");
 
     var request = new http.Request('POST', serverUrl.resolve('/loop?1'))
       ..maxRedirects = 2;
-    var future = request.send().catchError((AsyncError e) {
+    var future = request.send().catchError((e) {
       print("#maxRedirects test exception received");
       expect(e.error, isRedirectLimitExceededException);
       expect(e.error.redirects.length, equals(2));
     });
     future.catchError((_) {}).then(expectAsync1((_) {
       print("#maxRedirects test stopping server...");
       stopServer();
       print("#maxRedirects test server stopped");
     }));
 
@@ skipping 160 matching lines @@
   });
 
   group('#toString()', () {
     test('includes the method and URL', () {
       var request = new http.Request('POST', dummyUrl);
       expect(request.toString(), 'POST $dummyUrl');
     });
   });
 }