Use StatisticsMap interface

The interface lagged behind functionality, add the timing methods to it
so that it may be used again instead of the concrete classes. In doing
so make timing explicit when desired and do not include 0 loading times
in the statistics if they were never recorded in the first place.

Change-Id: I405512f3b52c15906b3644ca0321ee9c844a794c
4 files changed