anchor.diff:    if (!args.containsKey("output_dir")) throw "Please specify output_dir";
   
     var scriptFile = new File(options.script);
  -  var path = new Path(scriptFile.directorySync().path); 
  +  var path = new Path(scriptFile.directorySync().path);
     var rootPath = path.directoryPath.directoryPath;
   
     getSnapshotGenerationFile(options, args, rootPath).then((result) {
  
positive.code:  * --output_dir=val     The full path to the output_dir.
   * --dart2js_main=val   The path to the dart2js main script releative to root.
   */
  void main() { 
    Options options = new Options();
    var validArguments = ["--output_dir", "--dart2js_main"];
    var args = {};
  
negative.code: import 'dart:io';
  
  Future<String> getVersion(var options, var rootPath) {
    var os = Platform.operatingSystem;
    var suffix = os == 'windows' ? '.exe' : '';
    var checkedInBinary =
        rootPath.join(new Path('tools/testing/bin/$os/dart$suffix'));
    var versionPath = rootPath.append("tools").append("version.dart");
    return Process.run(checkedInBinary.toNativePath(),
                       [versionPath.toNativePath()])
        .then((result) {
          if (result.exitCode != 0) {
  