When a xdg-toplevel is reset, the window and actor are recreated, and
all state is cleared. When this happened, we earlied out from the
xdg-toplevel commit handler, which would mean that if the client had
queued frame callbacks when resetting, they'd be left in the pending
commit state, later hitting an assert as they were not handled.

Fix this by queuing the frame callbacks no the new actor, so that they
are emitted whenever the actor is eventually painted.

GNOME/mutter#240