Fix hosted tests 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 860 matching lines @@
       // GZIP it. 7zip doesn't support doing both as a single operation. Send
       // the output to stdout.
       args = ["a", "unused", "-tgzip", "-so", tarFile];
       return startProcess(command, args);
     }).then((process) {
       // Ignore 7zip's stderr. 7zip writes its normal output to stderr. We don't
       // want to show that since it's meaningless.
       //
       // TODO(rnystrom): Should log the stderr and display it if an actual error
       // occurs.
-      store(process.stdout, controller);
+      return store(process.stdout, controller);
     });
   }).catchError((e) {
     // We don't have to worry about double-signaling here, since the store()
     // above will only be reached if everything succeeds.
     controller.signalError(e.error, e.stackTrace);
     controller.close();
   });
   return new ByteStream(controller.stream);
 }
 
@@ skipping 40 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 Uri.parse(uri);
 }