anchor.diff:    parser.addFlag('dartium',
         help: 'run in dartium, test the app in app/', negatable: false);
     parser.addFlag('chrome',
  -      help: 'run in chrome, test the app in build/deploy-test-out/web/', negatable: false);
  +      help: 'an alias to --chrome-stable', negatable: false);
  +  parser.addFlag('chrome-stable',
  +      help: 'run in chrome stable, test the app in build/deploy-test-out/web/', negatable: false);
  +  parser.addFlag('chrome-dev',
  +      help: 'run in chrome dev, test the app in build/deploy-test-out/web/', negatable: false);
   
     parser.addOption('appPath', help: 'the application path to run');
     parser.addOption('browserPath', help: 'the path to chrome');
  
positive.code:   print('valid options:');
    print(parser.getUsage().replaceAll('\n\n', '\n'));
    print('');
    print('Generally, you should run this tool with either --dartium or --chrome. Optionally, you');
    print('can specify the browser to run the app in, and the application directory to launch.');
  }
  
  String _dartiumPath() {
  
negative.code:   if (FileSystemEntity.isFileSync(path)) {
      return new File(path).absolute.path;
    } else {
      throw 'unable to locate Dartium (${path})';
    }
  }
  
  String _chromeStablePath() {
    if (Platform.isLinux) {
      return '/usr/bin/google-chrome';
    } else if (Platform.isMacOS) {
      return '/Applications/Google Chrome.app/Contents/MacOS/Google Chrome';
    } else {
      // TODO: locate Chrome on Windows
      throw 'unable to locate Chrome; ${Platform.operatingSystem} not yet supported';
    }
  }
  
  String _chromeDevPath() {
    if (Platform.isLinux) {
      return '/usr/bin/google-chrome-unstable';
    } else {
      // TODO:
      throw 'unable to locate Chrome dev; ${Platform.operatingSystem} not yet supported';
    }
  }
  
  