Refactor Future constructors.

utils/pub/oauth2.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 oauth2;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:uri';
 
@@ skipping 86 matching lines @@
       return withClient(cache, fn);
     } else {
       throw error;
     }
   });
 }
 
 /// Gets a new OAuth2 client. If saved credentials are available, those are
 /// used; otherwise, the user is prompted to authorize the pub client.
 Future<Client> _getClient(SystemCache cache) {
-  return new Future.of(() {
+  return new Future.sync(() {
     var credentials = _loadCredentials(cache);
     if (credentials == null) return _authorize();
 
     var client = new Client(_identifier, _secret, credentials,
         httpClient: httpClient);
     _saveCredentials(cache, client.credentials);
     return client;
   });
 }
 
@@ skipping 79 matching lines @@
         response.statusCode = 404;
         response.close();
       }
     });
   })
   .then((client) {
     log.message('Successfully authorized.\n');
     return client;
   });
 }