Add short run mode and battery life in hours.

This adds several things:
1. Weighted average power draw that is intended to give an
   estimate of average draw for real life usage.
2. Calculation of battery life in hours for power draw while
   idle and for the weighted power draw.
3. Short run mode that runs fewer measurements in about 2.5
   minutes so it can be run per build.

BUG=chromium-os:34625
TEST=run_remote_test in both short and full mode
CQ-DEPEND=Ib7d8f1f1f89f0cba91231f4ca9dbd0d4e8d5570c

Change-Id: Ic9acd92ada337afe7ee257a647a3d06fb9e12892
Reviewed-on: https://gerrit.chromium.org/gerrit/33728
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Tested-by: Mark Koudritsky <kamrik@chromium.org>
Commit-Ready: Mark Koudritsky <kamrik@chromium.org>
2 files changed