Refactor Future constructors.

pkg/oauth2/test/utils.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 utils;
 
 import 'dart:async';
 import 'dart:collection' show Queue;
 
 import 'package:http/http.dart' as http;
@@ skipping 20 matching lines @@
     expect(completer.future, completes);
 
     _handlers.add((request) {
       completer.complete(null);
       return fn(request);
     });
   }
 
   Future<http.Response> _handleRequest(http.Request request) {
     if (_handlers.isEmpty) {
-      return new Future.immediate(new http.Response('not found', 404));
+      return new Future.value(new http.Response('not found', 404));
     } else {
       return _handlers.removeFirst()(request);
     }
   }
 }
 
 /// A matcher for AuthorizationExceptions.
 const isAuthorizationException = const _AuthorizationException();
 
 /// A matcher for functions that throw AuthorizationException.
@@ skipping 11 matching lines @@
 
 /// A matcher for functions that throw ExpirationException.
 const Matcher throwsExpirationException =
     const Throws(isExpirationException);
 
 class _ExpirationException extends TypeMatcher {
   const _ExpirationException() : super("ExpirationException");
   bool matches(item, MatchState matchState) =>
     item is oauth2.ExpirationException;
 }