anchor.diff:    }
   
     ZoneUnaryCallback registerUnaryCallback(Zone zone, f(arg)) {
  -    _CustomizedZone parent = _degelationTarget;
  +    _BaseZone parent = _degelationTarget;
       while (parent._specification.registerUnaryCallback == null) {
         parent = parent.parent;
       }
  
positive.code:   }
  
    Timer createPeriodicTimer(Zone zone, Duration period, void f(Timer timer)) {
      _CustomizedZone parent = _degelationTarget;
      while (parent._specification.createPeriodicTimer == null) {
        parent = parent.parent;
      }
  
negative.code:   }
  
    dynamic runBinary(Zone zone, f(arg1, arg2), arg1, arg2) {
      _BaseZone parent = _degelationTarget;
      while (parent._specification.runBinary == null) {
        parent = parent.parent;
      }
  