anchor.diff:  
     List<MarkerDelta> changes;
   
  -  MarkerChangeEvent(List<MarkerDelta> delta): changes = new UnmodifiableListView(delta);
  +  factory MarkerChangeEvent.fromList(List<MarkerDelta> deltas) {
  +    return new MarkerChangeEvent._(deltas.toList());
  +  }
  +
  +  MarkerChangeEvent._(List<MarkerDelta> delta): changes = new UnmodifiableListView(delta);
   
     /**
      * Checks if given [Resource] is present in the list of delta for marker changes
  
positive.code: 
    void _fireMarkerEvent(List<MarkerDelta> deltas) {
      if (_markersPauseCount == 0) {
        _markerController.add(new MarkerChangeEvent(deltas));
      } else {
        _makerChangeList.addAll(deltas);
      }
  
negative.code:   void resumeMarkerStream() {
      _markersPauseCount--;
      if (_markersPauseCount == 0 && _makerChangeList.isNotEmpty) {
        _markerController.add(new MarkerChangeEvent.fromList(_makerChangeList));
        _makerChangeList.clear();
      }
    }
  