Stop printing when stdout is closed.

tests/standalone/io/stdout_close_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 "package:expect/expect.dart";
+import "dart:io";
+
+void main() {
+  var dir = new Directory('').createTempSync();
+  stdout.close().then((_) {
+    var file = new File('${dir.path}/file');
+    var io = file.openSync(mode: FileMode.WRITE);
+    print("to file");
+    io.closeSync();
+    var content = file.readAsStringSync();
+    file.deleteSync();
+    dir.deleteSync();
+    Expect.equals("", content);
+  });
+}
+