Fix Windows dev_fs_test failure

runtime/bin/vmservice/vmservice_io.dart

 // Copyright (c) 2013, 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 vmservice_io;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 68 matching lines @@
   var file = await new File.fromUri(path);
   return await file.readAsBytes();
 }
 
 Future<List<Map<String,String>>> listFilesCallback(Uri dirPath) async {
   var dir = new Directory.fromUri(dirPath);
   var dirPathStr = dirPath.path;
   var stream = dir.list(recursive: true);
   var result = [];
   await for (var fileEntity in stream) {
+    var filePath = new Uri.file(fileEntity.path).path;
     var stat = await fileEntity.stat();
     if (stat.type == FileSystemEntityType.FILE &&
-        fileEntity.path.startsWith(dirPathStr)) {
+        filePath.startsWith(dirPathStr)) {
       var map = {};
-      map['name'] = '/' + fileEntity.path.substring(dirPathStr.length);
+      map['name'] = '/' + filePath.substring(dirPathStr.length);
       map['size'] = stat.size;
       map['modified'] = stat.modified.millisecondsSinceEpoch;
       result.add(map);
     }
   }
   return result;
 }
 
 _clearFuture(_) {
   serverFuture = null;
@@ skipping 47 matching lines @@
     Timer.run(() {});
   }
   scriptLoadPort.handler = _processLoadRequest;
   // Register signal handler after a small delay to avoid stalling main
   // isolate startup.
   _registerSignalHandlerTimer = new Timer(shortDelay, _registerSignalHandler);
   return scriptLoadPort;
 }
 
 _shutdown() native "VMServiceIO_Shutdown";