Use 'localhost' instead of '127.0.0.1', as IPv6 connections now can occur.

pkg/scheduled_test/lib/scheduled_server.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.
 
 library scheduled_test.scheduled_server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 import 'dart:uri';
@@ skipping 30 matching lines @@
 
   /// Creates a new server listening on an automatically-allocated port on
   /// localhost. [description] is used to refer to the server in debugging
   /// messages.
   factory ScheduledServer([String description]) {
     var id = _count++;
     if (description == null) description = 'scheduled server $id';
 
     var scheduledServer;
     scheduledServer = new ScheduledServer._(schedule(() {
-      return SafeHttpServer.bind("127.0.0.1", 0).then((server) {
+      return SafeHttpServer.bind("localhost", 0).then((server) {
         server.listen(scheduledServer._handleRequest,
             onError: (e) => currentSchedule.signalError(e));
         currentSchedule.onComplete.schedule(server.close);
         return server;
       });
     }, "starting '$description'"), description);
     return scheduledServer;
   }
 
   /// The port on which the server is listening.
@@ skipping 35 matching lines @@
             "when no more requests were expected.";
       }
       return _handlers.removeFirst().fn(request);
     }).catchError((e) {
       // Close the server so that we don't leave a dangling request.
       _server.then((s) => s.close());
       throw e;
     }), 'receiving ${request.method} ${request.uri}');
   }
 }