All the surfaces from all the X clients share the same wl_client so
wl_client_get_credentials can't be used to get the pid of the X
clients.
The shell may need to know the pid to be able to associate a surface
with e.g. a DBus service.
[Pekka: fixed trivial merge conflicts.]
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
a8e9b41578