Wall-clock time to generate the tile, in milliseconds.
Coarsening steps taken to fit maxTileBytes (see
TileOptions.reduceToFit); 0 when the tile fit at once.
One entry per source, in layer order.
Size of the encoded tile in bytes.
Tile column.
Tile row.
Tile zoom level.
Statistics of one generated tile, passed to RequestOptions.onTile.