Data usage buckets active time, parsing ISE.

When recording data usage, measure the actual active time, since
buckets can be quite long.  Offer incrementOperationCount() version
that reads thread stats tag for caller.  Rethrow any NPE as ISE
during stats parsing, which callers already handle.

Bug: 5171812, 5184508, 5180659
Change-Id: I6da80ccc0162be68bee279529e3a23b6f98ebd87