Big merge from experimental to bleeding edge.

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';
 import 'hosted_source.dart';
 import 'io.dart';
 import 'io.dart' as io show createTempDir;
 import 'log.dart' as log;
 import 'package.dart';
 import 'sdk_source.dart';
 import 'source.dart';
 import 'source_registry.dart';
@@ skipping 58 matching lines @@
     _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).chain((temp) {
+    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).chain((exists) {
+    return dirExists(tempDir).then((exists) {
       if (!exists) return new Future.immediate(null);
       return deleteDir(tempDir);
     });
   }
 }