Fix a number of issues with the process handling

tests/standalone/src/ProcessStdIOScript.dart

+// Copyright (c) 2011, 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.
+//
+// Utility script to echo stdin to stdout or stderr or both.
+
+main() {
+  var options = new Options();
+  if (options.arguments.length > 0) {
+    if (options.arguments[0] == "0") {
+      stdin.dataHandler = () => stdout.write(stdin.read());
+    } else if (options.arguments[0] == "1") {
+      stdin.dataHandler = () => stderr.write(stdin.read());
+    } else if (options.arguments[0] == "2") {
+      stdin.dataHandler = () {
+        var data = stdin.read();
+        stdout.write(data);
+        stderr.write(data);
+      };
+    }
+  }
+}