Background image usage on backdrop-filter test fails to trigger image load on all clients

[jimboolio]

As noted in background-image feature for samsung email clients, image load will not trigger unless there's at least one img element. This happens on K-9 Mail too, so it seems to be somewhat common behaviour.

Since this causes backdrop-filter.html test to not show the background image, it may be interpret as the feature not functioning, so it has a risk of causing incorrect data to be supplied to caniemail.

I'm wondering whether there should be an tag to trigger the image load or an alt text etc to signify that this may be the cause why the test may seem broken.

I detected the issue on K-9 Mail by resending the backdrop-image.html to myself again with one added img element.