Add console to dart:io for synchronus writing to stdout and stderr

tests/standalone/io/console_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:convert";
+import "dart:io";
+
+import "package:expect/expect.dart";
+
+void main() {
+  var script = Platform.script.resolve("console_script.dart").toFilePath();
+  Process.run(Platform.executable,
+              ['--checked', script],
+              stdoutEncoding: ASCII,
+              stderrEncoding: ASCII).then((result) {
+                  print(result.stdout);
+                  print(result.stderr);
+    Expect.equals(1, result.exitCode);
+    Expect.equals('stdout\nABCDEFGHIJKLM\n', result.stdout);
+    Expect.equals('stderr\nABCDEFGHIJKLM\n', result.stderr);
+  });
+}