Fix pub on windows.

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 63 matching lines @@
       ..closeSync();
   log.fine("Wrote text file $file.");
   return file;
 }
 
 /// Writes [stream] to a new file at path [file]. Will replace any file already
 /// at that path. Completes when the file is done being written.
 Future<String> createFileFromStream(Stream<List<int>> stream, String file) {
   log.io("Creating $file from stream.");
 
-  var stream = new File(file).openOutputStream();
-  return stream.pipe(wrapOutputStream(stream)).then((_) {
+  var outputStream = new File(file).openOutputStream();
+  return stream.pipe(wrapOutputStream(outputStream)).then((_) {
     log.fine("Created $file from stream.");
     return file;
   });
 }
 
 /// Creates a directory [dir].
 String createDir(String dir) {
   new Directory(dir).createSync();
   return dir;
 }
@@ skipping 764 matching lines @@
   const PubProcessResult(this.stdout, this.stderr, this.exitCode);
 
   bool get success => exitCode == 0;
 }
 
 /// 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 Uri.parse(uri);
 }