Refactor Future constructors.

utils/tests/pub/version_solver_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 pub_update_test;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:unittest/unittest.dart';
@@ skipping 463 matching lines @@
 class MockSource extends Source {
   final Map<String, Map<Version, Package>> _packages;
 
   final String name;
   bool get shouldCache => true;
 
   MockSource(this.name)
       : _packages = <String, Map<Version, Package>>{};
 
   Future<List<Version>> getVersions(String name, String description) {
-    return new Future.of(() => _packages[description].keys.toList());
+    return new Future.sync(() => _packages[description].keys.toList());
   }
 
   Future<Pubspec> describe(PackageId id) {
-    return new Future.of(() => _packages[id.name][id.version].pubspec);
+    return new Future.sync(() => _packages[id.name][id.version].pubspec);
   }
 
   Future<bool> install(PackageId id, String path) {
     throw 'no';
   }
 
   Package mockPackage(String description, String version,
       Map dependencyStrings) {
     // Build the pubspec dependencies.
     var dependencies = <PackageRef>[];
@@ skipping 44 matching lines @@
   };
 
   var match = new RegExp(r"(.*) from (.*)").firstMatch(description);
   if (match != null) {
     name = match[1];
     source = sourceNames[match[2]];
   }
 
   callback(isDev, name, source);
 }