Code review comment for lp:~andreas-pokorny/mir/add-timer-to-main-loop

I'm not going to block on this, but I am going to mention a concern: This adds another collection of unit tests that are slower than *any* acceptance tests. Vis:

$ ctest | grep sec$ | sort -n -b -k 7,7 -r | head -n 5
 73/191 Test #73: mir_unit_tests.BufferQueueTest.* ........................................... Passed 3.71 sec
137/191 Test #137: mir_unit_tests.MultiThreadedCompositor.* ................................... Passed 3.36 sec
 69/191 Test #69: mir_unit_tests.AsioMainLoopAlarmTest.* ..................................... Passed 1.08 sec
181/191 Test #181: mir_unit_tests.UdevWrapperDeathTest.* ...................................... Passed 0.51 sec
 16/191 Test #16: mir_acceptance_tests.ServerShutdown/OnSignal.* ............................. Passed 0.51 sec

"Unit tests" that take more than milliseconds are a cause for concern. As are tests that rely on the system clock.