anchor.diff:    final int _driverId;
   
     /// Client connected to the Dart VM running the Flutter application
  -  final VMServiceClient _serviceClient;
  +  ///
  +  /// You can use [VMServiceClient] to check VM version, flags and get
  +  /// notified when a new isolate has been instantiated. That could be
  +  /// useful if your application spawns multiple isolates that you
  +  /// would like to instrument.
  +  final VMServiceClient serviceClient;
   
     /// JSON-RPC client useful for sending raw JSON requests.
     final rpc.Peer _peer;
   
  -  /// The main isolate hosting the Flutter application
  -  final VMIsolate _appIsolate;
  +  /// The main isolate hosting the Flutter application.
  +  ///
  +  /// If you used the [registerExtension] API to instrument your application,
  +  /// you can use this [VMIsolate] to call these extension methods via
  +  /// [invokeExtension].
  +  final VMIsolate appIsolate;
   
     /// Whether to print communication between host and app to `stdout`.
     final bool _printCommunication;
  
positive.code:   /// Returns a [Future] that fires once the connection has been closed.
    Future<void> close() async {
      // Don't leak vm_service_client-specific objects, if any
      await _serviceClient.close();
      await _peer.close();
    }
  }
  
negative.code: /// Drives a Flutter Application running in another process.
  class FlutterDriver {
    /// Creates a driver that uses a connection provided by the given
    /// [serviceClient], [_peer] and [appIsolate].
    @visibleForTesting
    FlutterDriver.connectedTo(
      this.serviceClient,
      this._peer,
      this.appIsolate, {
      bool printCommunication = false,
      bool logCommunicationToFile = true,
    }) : _printCommunication = printCommunication,
  