Revert "Make stdout/stderr async"

tests/standalone/io/stdio_nonblocking_script.dart

+// Copyright (c) 2015, 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:async";
+import "dart:io";
+
+class Message {
+  final message;
+  Message(this.message);
+  toString() => message;
+}
+
+void test(IOSink sink) {
+  sink.add([65, 66, 67]);
+  sink.write('DEF');
+  sink.writeAll(['GH', 'I']);
+  sink.writeCharCode(74);
+  sink.writeln('KLM');
+}
+
+void main(List<String> arguments) {
+  stdout.nonBlocking.writeln('stdout');
+  stderr.nonBlocking.writeln('stderr');
+  stdout.nonBlocking.writeln();
+  stderr.nonBlocking.writeln();
+  stdout.nonBlocking.writeln(new Message('tuodts'));
+  stderr.nonBlocking.writeln(new Message('rredts'));
+  test(stdout.nonBlocking);
+  test(stderr.nonBlocking);
+  Future.wait([stdout.nonBlocking.close(),
+               stderr.nonBlocking.close()])
+      .then((_) => exit(1));
+}