Make Source.getDirectory synchronous.

lib/src/command/cache_add.dart

 // Copyright (c) 2014, 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.command.cache_add;
 
 import 'dart:async';
 
 import 'package:pub_semver/pub_semver.dart';
 
@@ skipping 52 matching lines @@
     var versions = pubspecs.map((pubspec) => pubspec.version)
         .where(constraint.allows).toList();
 
     if (versions.isEmpty) {
       // TODO(rnystrom): Show most recent unmatching version?
       fail("Package $package has no versions that match $constraint.");
     }
 
     downloadVersion(version) async {
       var id = new PackageId(package, source.name, version, package);
-      if (await cache.contains(id)) {
+      if (cache.contains(id)) {
         // TODO(rnystrom): Include source and description if not hosted.
         // See solve_report.dart for code to harvest.
         log.message("Already cached ${id.name} ${id.version}.");
         return null;
       }
 
       // Download it.
       await source.downloadToSystemCache(id);
     }
 
     if (argResults["all"]) {
       // Install them in ascending order.
       versions.sort();
       await Future.forEach(versions, downloadVersion);
     } else {
       // Pick the best matching version.
       versions.sort(Version.prioritize);
       await downloadVersion(versions.last);
     }
   }
 }