metrics_daemon: fix parsing of zram sysfs

The only real change is in ReadFileToUint64.  The other changes
appease the updated pre-commit checks.

BUG=chromium:390334
TEST=ran manually, checked syslog, checked chrome://histograms

Change-Id: I5ca10aab03697aa8fd64c5dd51ca64911e8d2a76
Reviewed-on: https://chromium-review.googlesource.com/206285
Tested-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Daniel Erat <derat@chromium.org>
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>
2 files changed
tree: f77b83099430d1a03f16adc5bd6fe7e41e03846a
  1. metrics/