getDataToDraw(tile) {
        const cache = tile.getCache(tile.cacheKey);
        if (!cache) {
            $.console.warn("Attempt to draw tile %s when not cached!", tile);
            return undefined;
        }
        const dataCache = cache.getDataForRendering(this, tile);
        return dataCache && dataCache.data;
    }
Check a particular cache record is compatible.
This function _MUST_ be called: if it returns a falsey
value, the rendering _MUST NOT_ proceed. It should
await next animation frames and check again for availability.
@param {OpenSeadragon.Tile} tile
@return {any|undefined} undefined if cache not available, compatible data otherwise.