Pass BatteryChargeMode* prefs to ChromeOS

Subscribe on BatteryChargeMode, BatteryChargeCustomStartCharging and
BatteryChargeCustomStopCharging local state prefs and pass them to
ChromeOS side.

BUG=b:127456312
TEST=chromeos_unittests && ash_unittests

Change-Id: I9b6b3a1a85d48d49aa9101d67f8a98db6823cdf9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1572342
Commit-Queue: Oleh Lamzin <lamzin@google.com>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653946}
5 files changed