code: function(evt) {
      var poly = this._shape || this._poly;
      var marker = evt.target;
      poly.fire('mousedown', L.Util.extend(evt, {
        containerPoint: L.DomUtil.getPosition(marker._icon)
          .add(poly._map._getMapPanePos())
      }));
    }
docs: Start dragging through the marker
  @param  {L.MouseEvent} evt