Make IOSink implement StringSink

tests/standalone/io/file_output_stream_test.dart

Index: tests/standalone/io/file_output_stream_test.dart
diff --git a/tests/standalone/io/file_output_stream_test.dart b/tests/standalone/io/file_output_stream_test.dart
index 645399ab55d35ceb2b2834cce71896d69bdf2d0f..b1d81fcb2c5059c72fb59ec301de211d9bf03b29 100644
--- a/tests/standalone/io/file_output_stream_test.dart
+++ b/tests/standalone/io/file_output_stream_test.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.
 // Testing file input stream, VM-only, standalone test.
@@ -21,7 +21,7 @@ void testOpenOutputStreamSync() {
   file.createSync();
   IOSink x = file.openWrite();
   var data = [65, 66, 67];
-  x.add(data);
+  x.writeBytes(data);
   x.close();
   x.done.then((_) {
     Expect.listEquals(file.readAsBytesSync(), data);