Change all File APIs to make the mode and encoding arguments named

utils/lib/file_system_vm.dart

Index: utils/lib/file_system_vm.dart
diff --git a/utils/lib/file_system_vm.dart b/utils/lib/file_system_vm.dart
index 12fb712873de0e40654cfab2daf53d33f4431255..7c09b7014e012f8c35487ae0c651bece05feaee6 100644
--- a/utils/lib/file_system_vm.dart
+++ b/utils/lib/file_system_vm.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -12,7 +12,7 @@ import 'dart:utf';
 /** File system implementation using the vm api's. */
 class VMFileSystem implements FileSystem {
   void writeString(String path, String text) {
-    var file = new File(path).openSync(FileMode.WRITE);
+    var file = new File(path).openSync(mode: FileMode.WRITE);
     file.writeStringSync(text);
     file.closeSync();
   }