This includes ClockMonotonicNanoseconds() and SleepNanoseconds().
SleepNanoseconds() is like base::PlatformThread::Sleep(), but
PlatformThread is not in mini_chromium and I’m not keen on adding it
because I’m not sold on the interface. I’m not convinced Sleep() belongs
there, and I don’t want to have to bring all of base::Time* along for
the ride.
TEST=util_test Clock.*:MachMessageServer.*:ServiceManagement.*
R=rsesek@chromium.org
Review URL: https://codereview.chromium.org/597533002
