I am working on adding a test to ensure Weston repaints damage
correctly, where I rely on Weston repainting exactly and only the damage
submitted by a client. That means I have to stop screenshooting from
damaging everything automatically. Doing that, I noticed that
screenshots on DRM-backend could theoretically get stuck if I do that.
So test for it.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
