This seems like a better name, and will not conflict if someone later
extends wl_surface with a request scaler_set (yeah, unlikely).
This code was written by Jonny Lamb, I just diffed his branches and made
a patch for Weston.
Cc: Jonny Lamb <jonny.lamb@collabora.co.uk>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>