Use destructuring assignments for named parameters (#180)

bin/devrun.dart

 #!/usr/bin/env 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.
 
 /// Runs io.js with dev_compiler's generated code.
 library dev_compiler.bin.devrun;
 
 import 'dart:io';
 
@@ skipping 70 matching lines @@
             .join("\n")}
     <script>$startStatement</script>
     </body></html>
   ''');
 
   stderr.writeln(
       'Wrote $htmlOutput. It can be opened in Chrome Dev with the following flags:\n'
       '--js-flags="--harmony-arrow-functions '
       '--harmony-classes '
       '--harmony-computed-property-names '
+      '--harmony_destructuring '
       '--harmony-spreadcalls"'
       '\n');
 }