Fix fullscreen test on IE11
Fix fullscreen test on IE11

Iced-Tea/openseadragon,ricochet2200/openseadragon,janelia-flyem/openseadragon,shaunstanislaus/openseadragon,TMUND/openseadragon,goofwear/openseadragon,daverome/openseadragon,lidasong2014/openseadragon,LarissaSmith/openseadragon,seanich/openseadragon,openseadragon/openseadragon,avandecreme/openseadragon,openseadragon/openseadragon,jmnetus/openseadragon,mcanthony/openseadragon,msalsbery/openseadragon,ricochet2200/openseadragon,Iced-Tea/openseadragon,shaunstanislaus/openseadragon,jmnetus/openseadragon,goofwear/openseadragon,seanich/openseadragon,rdlester/openseadragon,LarissaSmith/openseadragon,lidasong2014/openseadragon,janelia-flyem/openseadragon,TMUND/openseadragon,msalsbery/openseadragon,avandecreme/openseadragon,daverome/openseadragon,rdlester/openseadragon,mcanthony/openseadragon