Revert "Update event assertions."
Revert "Update event assertions."

This reverts commit fd15789f6fb851257d59f616d685a888f651e872.

openseadragon/openseadragon,LarissaSmith/openseadragon,openseadragon/openseadragon,LarissaSmith/openseadragon,seanich/openseadragon,seanich/openseadragon