Fix pub tests.

utils/pub/system_cache.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 system_cache;
 
 import 'dart:io';
 import 'dart:async';
 
 import 'git_source.dart';
@@ skipping 55 matching lines @@
   /// == false` to the system cache.
   Future<Package> install(PackageId id) {
     if (!id.source.shouldCache) {
       throw new ArgumentError("Package $id is not cacheable.");
     }
 
     var pending = _pendingInstalls[id];
     if (pending != null) return pending;
 
     var future = id.source.installToSystemCache(id)
-        .whenComplete(() => _pendingInstalls.remove(id));
+        .whenComplete(() { _pendingInstalls.remove(id); });
     _pendingInstalls[id] = future;
     return future;
   }
 
   /// Create a new temporary directory within the system cache. The system
   /// cache maintains its own temporary directory that it uses to stage
   /// packages into while installing. It uses this instead of the OS's system
   /// temp directory to ensure that it's on the same volume as the pub system
   /// cache so that it can move the directory from it.
   Future<Directory> createTempDir() {
     return ensureDir(tempDir).then((temp) {
       return io.createTempDir(join(temp, 'dir'));
     });
   }
 
   /// Delete's the system cache's internal temp directory.
   Future deleteTempDir() {
     log.fine('Clean up system cache temp directory $tempDir.');
     return dirExists(tempDir).then((exists) {
       if (!exists) return new Future.immediate(null);
       return deleteDir(tempDir);
     });
   }
 }