anchor.diff:        buildSourceMap: argResults['source-map'] as bool,
         jsUrl: path.toUri(output).toString(),
         mapUrl: path.toUri(output + '.map').toString(),
  -      bazelMapping: options.bazelMapping);
  +      bazelMapping: options.bazelMapping,
  +      customScheme: multiRootScheme);
   
     outFiles.add(file.writeAsString(jsCode.code));
     if (jsCode.sourceMap != null) {
  
positive.code:   // 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 fileSystem = MultiRootFileSystem(
        customScheme, [Uri.base], StandardFileSystem.instance);
  
    Uri toCustomUri(Uri uri) {
      if (uri.scheme == '') {
        return Uri(scheme: customScheme, path: '/' + uri.path);
      }
      return uri;
    }
  
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);
  