Make GetBytesAllocatedEver() monotonic

Make the _freed_ever_ counters atomic, since they can apparently
be read concurrently. This removes the data race.

We enforce monotonicity in a brute force way, which is probably good
enough here. The results remain approximate, as they always were.

Bug: 142328050
Test: Built AOSP.

Change-Id: Ifb8520d0edee7cadadc62f59992c6d9b67251c32
2 files changed