Reapply revert of "Make stdout/stderr async"

tests/standalone/io/console_script.dart

-// Copyright (c) 2014, 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.
-
-import "dart:io";
-
-class Message {
-  final message;
-  Message(this.message);
-  toString() => message;
-}
-
-void test(ConsoleSink sink) {
-  sink.add([65, 66, 67]);
-  sink.write('DEF');
-  sink.writeAll(['GH', 'I']);
-  sink.writeCharCode(74);
-  sink.writeln('KLM');
-}
-
-void main(List<String> arguments) {
-  console.log('stdout');
-  console.error('stderr');
-  console.log();
-  console.error();
-  console.log(new Message('tuodts'));
-  console.error(new Message('rredts'));
-  test(console.log);
-  test(console.error);
-  exit(1);
-}