Code review comment for lp:~vanvugt/mir/double

Excellent point Alexandros. That's now fixed with extra tests for the scenarios you describe.

Unfortunately I just realized that there's another situation that probably needs fixing: A system with a single slow-ticking client (like a clock) won't ever know that the compositor is capable of running any faster than the client is, and so will classify the client as slow --> triple buffers prematurely.