Make Source.getDirectory synchronous.

test/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_upgrade_test;
 
 import 'dart:async';
 
 import 'package:pub/src/lock_file.dart';
 import 'package:pub/src/log.dart' as log;
@@ skipping 1374 matching lines @@
   final hasMultipleVersions = true;
 
   MockSource(this.name);
 
   dynamic parseDescription(String containingPath, description,
                              {bool fromLockFile: false}) => description;
 
   bool descriptionsEqual(description1, description2) =>
       description1 == description2;
 
-  Future<String> getDirectory(PackageId id) {
-    return new Future.value('${id.name}-${id.version}');
-  }
+  String getDirectory(PackageId id) => '${id.name}-${id.version}';
 
   Future<List<Pubspec>> getVersions(String name, String description) {
     return new Future.sync(() {
       // Make sure the solver doesn't request the same thing twice.
       if (_requestedVersions.contains(description)) {
         throw new Exception('Version list for $description was already '
             'requested.');
       }
 
       _requestedVersions.add(description);
@@ skipping 124 matching lines @@
   }
 
   var source = "mock1";
   if (match[7] != null) {
     source = match[7];
     if (source == "root") source = null;
   }
 
   return new PackageId(name, source, parsedVersion, description);
 }