Use accurate time to update Chronometer value

Fixes: 357576142
Flag: EXEMPT bugfix

Chronometer used postDelayed(1000ms) to update its time.
Over the course of many seconds, this could skew until
the time jumps more than one second.

This CL uses the time elapsed since the start to determine
when the Chronometer should update. Even if an update is
delayed, it will update after a shorter time on the following
frame.

Test: new test
Change-Id: I0c3210002af094f1e057a450408fcf7455934c66