Fix getScaleForEdgeSmoothing with image tile source.
Fix getScaleForEdgeSmoothing with image tile source.

avandecreme/openseadragon,jmnetus/openseadragon,msalsbery/openseadragon,rdlester/openseadragon,seanich/openseadragon,LarissaSmith/openseadragon,openseadragon/openseadragon,rdlester/openseadragon,msalsbery/openseadragon,jmnetus/openseadragon,LarissaSmith/openseadragon,openseadragon/openseadragon,seanich/openseadragon,avandecreme/openseadragon