Add, test, and use clock utilities

Add, test, and use clock utilities.

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

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/8decf86db833551f996760772c222ce8feafa9e4

[Mark Mentovai, 2014-09-23 14:01:02]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Robert Sesek, 2014-09-24 17:55:14]

LGTM

[Mark Mentovai, 2014-09-24 18:08:52]

Committed patchset #3 (id:40001) manually as 8decf86db833 (presubmit
successful).