Since commit 6183eb3632 we disabled swap
throttling in favour of being driven by the GDK frame clock (and thus by
the compositor).
Compositors may decide to unredirect full screen windows to avoid the
performance penalty of the additional copy, especially on X11, which
means that a Clutter application marked as full screen is not going to
be driven by the compositor, and it's not going to be throttled by the
underlying GL machinery. This has a performance impact on constrained
platforms.
For this reason, we should re-enable swap throttling when the window is
full screen.
As the change was introduced especially because of Wayland, we should
check that we're not running as clients under a Wayland compositor; if
we do, we always keep swap throttling disabled, as the compositor will
always manage our output, even when full screen.
c624230a8a