anchor.diff:  
     @override
     DeviceLogReader getLogReader({ApplicationPackage app}) {
  +    assert(app is IOSApp);
       _logReaders ??= <ApplicationPackage, _IOSSimulatorLogReader>{};
       return _logReaders.putIfAbsent(app, () => new _IOSSimulatorLogReader(this, app));
     }
  
positive.code:       final String content = match.group(4);
  
        // Filter out non-Flutter originated noise from the engine.
        if (category != 'Runner')
          return null;
  
        if (tag != null && tag != '(Flutter)')
  
negative.code: class _IOSSimulatorLogReader extends DeviceLogReader {
    String _appName;
  
    _IOSSimulatorLogReader(this.device, IOSApp app) {
      _linesController = new StreamController<String>.broadcast(
        onListen: _start,
        onCancel: _stop
  