This patch basically restores the logic from 1.6. There we assumed that
glXCopySubBuffer won't tear and thus only needs to be throttled to the
framerate, while glBlitFramebuffer needs to always wait to avoid
tearing.
With Nvidia drivers specifically we have seen that glBlitFramebuffer is
not synchronized. Eventually the plan is that Cogl will actually take
into consideration the underlying driver/hw vendor and driver version
and we may want to only mark glBlitFramebuffer un-synchronized on
Nvidia.
https://bugzilla.gnome.org/show_bug.cgi?id=659360
Reviewed-by: Robert Bragg <robert@linux.intel.com>
671a4dfb34