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:     if (response['isError'])
        throw new DriverError('Error in Flutter application: ${response['response']}');
      return response['response'];
    }
  
    /// Checks the status of the Flutter Driver extension.
  
negative.code:   /// 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,
          _logCommunicationToFile = logCommunicationToFile,
          _driverId = _nextDriverId++;
  
    static const String _kFlutterExtensionMethod = 'ext.flutter.driver';
    static const String _kSetVMTimelineFlagsMethod = '_setVMTimelineFlags';
    static const String _kGetVMTimelineMethod = '_getVMTimeline';
    static const Duration _kRpcGraceTime = const Duration(seconds: 2);
  
    static int _nextDriverId = 0;
  
    /// Connects to a Flutter application.
    ///
    /// Resumes the application if it is currently paused (e.g. at a breakpoint).
  