I think this has to do with the content in question being rendered on the GPU separately from the website itself. Historically I recall this being an issue with

I think this has to do with the content in question being rendered on the GPU separately from the website itself. Historically I recall this being an issue with all forms of video display in some browsers but at this point (with website rendering generally being at least in part GPU accelerated) it shouldn't be an issue I think unless for some reason the browser is set up to use software rendering for the website itself. I do faintly recall not being able to see video player content in screenshots taken on Ubuntu (but the player itself could take snapshots just fine) because of a divide like this some years ago.