code: function(evt) {
      var x = evt.containerPoint.x;
      var y = evt.containerPoint.y;
  
      var dx = x - this._startPoint.x;
      var dy = y - this._startPoint.y;
  
      if (!this._path._dragMoved && (dx || dy)) {
        this._path._dragMoved = true;
        this._path.fire('dragstart');
      }
  
      this._matrix[4] += dx;
      this._matrix[5] += dy;
  
      this._startPoint.x = x;
      this._startPoint.y = y;
  
      this._path._applyTransform(this._matrix);
      this._path.fire('drag');
      L.DomEvent.stop(evt.originalEvent);
    }
docs: Dragging
  @param  {L.MouseEvent} evt