Revert "Revert "Make stdout/stderr async""

tests/standalone/io/stdout_stderr_terminal_test.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.
-
-import "dart:io";
-
-import "package:expect/expect.dart";
-
-void testTerminalSize(std) {
-  if (std.hasTerminal) {
-    Expect.notEquals(0, std.terminalColumns);
-    Expect.notEquals(0, std.terminalLines);
-  } else {
-    Expect.throws(() => std.terminalColumns, (e) => e is StdoutException);
-    Expect.throws(() => std.terminalLines, (e) => e is StdoutException);
-  }
-}
-
-
-void main() {
-  testTerminalSize(stdout);
-  testTerminalSize(stderr);
-}