Stop working around issue 7790 in pub.

utils/pub/io.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.
 
 /// Helper functionality to make working with IO easier.
 library io;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
@@ skipping 731 matching lines @@
     completer.completeError(e.error, e.stackTrace);
   });
   return completer.future;
 }
 
 /// Creates a temporary directory and passes its path to [fn]. Once the [Future]
 /// returned by [fn] completes, the temporary directory and all its contents
 /// will be deleted.
 Future withTempDir(Future fn(String path)) {
   var tempDir;
-  return asyncWhenComplete(createTempDir().then((dir) {
+  return createTempDir().then((dir) {
     tempDir = dir;
     return fn(tempDir.path);
-  }), () {
+  }).whenComplete(() {
     log.fine('Cleaning up temp directory ${tempDir.path}.');
     return deleteDir(tempDir);
   });
 }
 
 /// Tests whether or not the git command-line app is available for use.
 Future<bool> get isGitInstalled {
   if (_isGitInstalledCache != null) {
     // TODO(rnystrom): The sleep is to pump the message queue. Can use
     // Future.immediate() when #3356 is fixed.
@@ skipping 251 matching lines @@
 Directory _getDirectory(entry) {
   if (entry is Directory) return entry;
   return new Directory(entry);
 }
 
 /// Gets a [Uri] for [uri], which can either already be one, or be a [String].
 Uri _getUri(uri) {
   if (uri is Uri) return uri;
   return new Uri.fromString(uri);
 }