anchor.diff:    // lib folder). The following [FileSystem] will resolve those references to
     // the correct location and keeps the real file location hidden from the
     // front end.
  -  var customScheme = 'org-dartlang-app';
  +  var multiRootScheme = argResults['multi-root-scheme'] as String;
  +
     var fileSystem = MultiRootFileSystem(
  -      customScheme, [Uri.base], StandardFileSystem.instance);
  +      multiRootScheme,
  +      (argResults['multi-root'] as Iterable<String>)
  +          .map(Uri.base.resolve)
  +          .toList(),
  +      StandardFileSystem.instance);
   
     Uri toCustomUri(Uri uri) {
       if (uri.scheme == '') {
  -      return Uri(scheme: customScheme, path: '/' + uri.path);
  +      return Uri(scheme: multiRootScheme, path: '/' + uri.path);
       }
       return uri;
     }
  
positive.code:       buildSourceMap: argResults['source-map'] as bool,
        jsUrl: path.toUri(output).toString(),
        mapUrl: path.toUri(output + '.map').toString(),
        bazelMapping: options.bazelMapping);
  
    outFiles.add(file.writeAsString(jsCode.code));
    if (jsCode.sourceMap != null) {
  
negative.code:         help: 'emit API summary in a .js.txt file', defaultsTo: true)
      // TODO(jmesserly): add verbose help to show hidden options
      ..addOption('dart-sdk-summary',
          help: 'The path to the Dart SDK summary file.', hide: true)
      ..addOption('multi-root-scheme',
          help: 'The custom scheme to indicate a multi-root uri.',
          defaultsTo: 'org-dartlang-app')
      ..addMultiOption('multi-root',
          help: 'The directories to search when encountering uris with the '
              'specified multi-root scheme.',
          defaultsTo: [Uri.base.toFilePath()]);
    SharedCompilerOptions.addArguments(argParser);
  
    var declaredVariables = parseAndRemoveDeclaredVariables(args);
  