metrics_daemon: add zram stats collection
Memory compression stats are being collected by Chrome, but it
is more natural to do it here since they are system-wide rather than
In addition, this provides better granularity for the compression ratio
(percents, from 100% to 600%) since we're especially interested in the
distribution of values between 1 and 2, and currently these all fall
in the same bucket.
Finally, we collect more interesting stats on zero pages.
TEST=unit testing, checked about:histograms
Reviewed-by: Luigi Semenzato <firstname.lastname@example.org>
Commit-Queue: Luigi Semenzato <email@example.com>
Tested-by: Luigi Semenzato <firstname.lastname@example.org>
3 files changed