- Use the appropriate UMA macros.
- The hard fault counters can sometime overflow, handle this.
- Rename the UMA metrics to Memory.Experimental
- The swapping threshold was too low, it has been guesstimated locally
  with a sampling rate of 1Hz but the monitor runs at 0.5Hz, so the
  value has to be higher.

Bug: 771478
Change-Id: I3038a55f97b78bef1e4a17793d7a1a8196a89230
TBR: chrisha@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/745703


Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512753}