Implement support for synchronous subsurfaces commits. This means that
the client can, by calling wl_subsurface.set_sync, cause its surface
state to be commited not until its parent commits.
This will mean there will be will potentially be one more surface state
(regions, buffer) at the same time: the active surface state, the mutable
pending surface state, and the immutable surface state that was pending
on last surface commit.
Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
https://bugzilla.gnome.org/show_bug.cgi?id=705502
4f4b1bfc37
