[DebugCounters] Keep track of total counts

Authored by george.burgess.iv on Jul 23 2018, 2:49 PM.


[DebugCounters] Keep track of total counts

This patch makes debug counters keep track of the total number of times
we've called shouldExecute for each counter, so it's easier to build
automated tooling on top of these.

A patch to print these counts is coming soon.

Patch by Zhizhou Yang!

Differential Revision: https://reviews.llvm.org/D49560

llvm-svn: 337748