anchor.diff:   */
   class ChromeService extends Service {
     String serviceId = "chrome";
  -  ChromeService(_IsolateHandler handler) : super(handler);
  +  ChromeService(Services services, _IsolateHandler handler)
  +      : super(services, handler);
   
     // For incoming (non-requested) actions.
     void _receiveAction(ActionEvent event) {
  
positive.code: class ExampleService extends Service {
    String serviceId = "example";
  
    ExampleService(_IsolateHandler handler) : super(handler);
  }
  
  /**
  
negative.code: abstract class Service {
    static int _topCallId = 0;
  
    Services _services;
    _IsolateHandler _isolateHandler;
  
    String get serviceId;
  
    Service(this._services, this._isolateHandler);
  
    String _getNewCallId() => "host_${_topCallId++}";
  
  