Code review comment for lp:~vanvugt/mir/swap-then-flip

Cemils comment was discussed in IRC. I believe the driver handles this synchronization.

I'm not so sure if this is a real optimization, e.g. the expensive part of swap is the flush and presumably rendering was already happening in the background anyway. I agree this seems conceptually correct though: Finish GL Rendering, Update EGL State, Mark buffer as new front buffer.

Please get review from someone with better knowledge of this than me, e.g. Alf, Chris, ...?