L.TileLayer.GeoJSON.Multi = L.TileLayer.GeoJSON.extend({
  addTileData: function(json, tilePoint) {

   for (var featureName in json) {
     var geojson = json[featureName];
     L.TileLayer.GeoJSON.prototype.addTileData.apply(geojson, tilePoint);
   }
  }
});