minor refactoring in chunkification
minor refactoring in chunkification

pnorman/carto,stefanklug/carto,whitelynx/carto,gravitystorm/carto,CartoDB/carto,mapbox/carto,midnightcomm/carto,clhenrick/carto,madeinqc/carto,1ec5/carto,tomhughes/carto,CartoDB/carto