libweston: Clip damage to paint node visible region
commit 79212ba9 fixed a bug by introducing a new one.
Before that point we could clip paint node damage to stale visibility data. After that point we post damage for occluded views, leading to large amounts of pointless drawing.
Add back the clip to visible region, in weston_output_flush_damage_for_plane(), where we have up to date visibility region information.
fixes 79212ba9
Signed-off-by: Derek Foreman derek.foreman@collabora.com