Artificial performance limitation

[Daniel van Vugt]

This bug and its sister bug are driving me crazy:
https://bugs.launchpad.net/mir/+bug/1388490
https://bugs.launchpad.net/mir/+bug/1377872

I can see in both cases that the frame rate ceiling is arbitrary and 
temporary. It has nothing at all to do with the power of the host. And 
the workaround that fixes the problem in both cases is a bit crazy.

I've so far investigated theories around:
   * buffer lifetimes
   * Mesa/intel GL batching bugs
   * lock contention (locks held too long)
   * power management modes
   * Mir socket/protocol bottlenecks

All the theories have some merit but I am not making progress. If you 
are (un)lucky enough to be able to reproduce either bug then please join 
in. More data points are required.

- Daniel