Timing::measure(): handle missing marks better

Timing::measure(): handle missing marks better

Currently Timing::measure() does not check that the requested start and end
marks exist, causing it to return bogus values without any indication that
something has gone wrong. Fix this by logging and error and returning false
in case either the start or end markers do not exist. To make it possible to
log, make Timing implement the LoggerAware interface.

Change-Id: I75af5273e9a8a52b31d0af1de206b0d8a4c82fbc