Annotate ChargingStatus as a state atom.

Charging status is different from plugged status and can be used as a
state for certain metrics.

Bug: 140496920
Bug: 143495340
Bug: 145838040
Test: bit statsd_test:*
Change-Id: I1ef41191588b6d26346323203dabe488d488c131
1 file changed
tree: c8bcddc128dfe41a685affad1a0f3b5615f09eef
  1. atom_field_options.proto
  2. atoms.proto