Starting in Ubuntu 17.10, totem (and some other apps like gnome-maps) use Wayland subsurfaces by default. This means the video (or maps) rectangle are able to redraw without redrawing the window decorations and saves a lot of CPU.
A side-effect of this is that screenshots didn't seem to work any more. However I believe that's just going to be a bug in gnome-shell/mutter, for not being able to screenshot its own Wayland subsurfaces.
Starting in Ubuntu 17.10, totem (and some other apps like gnome-maps) use Wayland subsurfaces by default. This means the video (or maps) rectangle are able to redraw without redrawing the window decorations and saves a lot of CPU.
A side-effect of this is that screenshots didn't seem to work any more. However I believe that's just going to be a bug in gnome-shell/mutter, for not being able to screenshot its own Wayland subsurfaces.