If no extent use the buffered extent of the tile for composite
If no extent use the buffered extent of the tile for composite

tomhughes/node-mapnik,CartoDB/node-mapnik,mapnik/node-mapnik,tomhughes/node-mapnik,CartoDB/node-mapnik,CartoDB/node-mapnik,mapnik/node-mapnik,langateam/node-mapnik,langateam/node-mapnik,tomhughes/node-mapnik,CartoDB/node-mapnik,mapnik/node-mapnik,tomhughes/node-mapnik,mapnik/node-mapnik,mapnik/node-mapnik,CartoDB/node-mapnik,langateam/node-mapnik,tomhughes/node-mapnik,langateam/node-mapnik,langateam/node-mapnik