anchor.diff:  
   import 'dart:async';
   import 'dart:convert';
  +import 'package:file/file.dart' as f;
   import 'dart:io';
   import 'package:json_rpc_2/json_rpc_2.dart' as rpc;
   import 'package:meta/meta.dart';
  +import 'package:path/path.dart' as p;
   import 'package:vm_service_client/vm_service_client.dart';
   import 'package:web_socket_channel/io.dart';
   
  +import 'common.dart';
   import 'error.dart';
   import 'find.dart';
  +import 'frame_sync.dart';
   import 'gesture.dart';
   import 'health.dart';
   import 'input.dart';
   import 'message.dart';
   import 'render_tree.dart';
  -import 'frame_sync.dart';
   import 'timeline.dart';
   
   /// Timeline stream identifier.
  
positive.code:       isolate = await vm.isolates.first.loadRunnable();
      }
  
      FlutterDriver driver = new FlutterDriver.connectedTo(client, connection.peer, isolate);
  
      // Attempts to resume the isolate, but does not crash if it fails because
      // the isolate is already resumed. There could be a race with other tools,
  
negative.code:     return driver;
    }
  
    /// The unique ID of this driver instance.
    final int _driverId;
    /// Client connected to the Dart VM running the Flutter application
    final VMServiceClient _serviceClient;
    /// JSON-RPC client useful for sending raw JSON requests.
    final rpc.Peer _peer;
    /// The main isolate hosting the Flutter application
    final VMIsolateRef _appIsolate;
    /// Whether to print communication between host and app to `stdout`.
    final bool _printCommunication;
    /// Whether to log communication between host and app to `flutter_driver_commands.log`.
    final bool _logCommunicationToFile;
  
    Future<Map<String, dynamic>> _sendCommand(Command command) async {
      Map<String, dynamic> response;
      try {
        Map<String, String> serialized = command.serialize();
        _logCommunication('>>> $serialized');
        response = await _appIsolate
            .invokeExtension(_kFlutterExtensionMethod, serialized)
            .timeout(command.timeout + _kRpcGraceTime);
        _logCommunication('<<< $response');
      } on TimeoutException catch (error, stackTrace) {
        throw new DriverError(
          'Failed to fulfill ${command.runtimeType}: Flutter application not responding',
  