power_BatteryCharge currently provides ability to track battery charging profile of CrOS device in S0.  Some enhancements to the test would allow us to automate & validate certain other hwqual values.

Some of the necessary additions to make the test more useful would be:
1. Ability to be run from any system power state (S0, S3, S5).  Currently the test only supports S0.  Providing S3 support should be easy enough using wake sources available but S5 will be non-trivial as will need to explore how/if autotest client tests manage restart.  If thats not possible then migrating this test to server side may be necessary.

2. Add Charging state control directly to manage starting state-of-charge.  Currently the test relies on legacy suite usage (control.power_build) to pair discharging tests with calls to power_BatteryCharge.  Would be nice if test could manage discharge load so it can target controlled discharge scenarios followed by charging as well as mimic workloads during charging.

3. keyvals.  Lets break them into two groups: 
3a. Those that give more detail of charging profile
- charging graph and/or breakdown of linear regions
- discharging graph (if managed by test)
3b. Those that detail things that impact charging profile.
- temperatures
- workload during charge (c-states)
- externally connected devices

Hope is that once completing these tasks we'll be able to run this test to do things like:

- Compute total charge time in S0 with workload (probably current =~ POWER_SUPPLY_CHARGE_FULL_DESIGN / Xhrs)
- Compute total charge time in S3
- Compute fast charge times(15min, 1hr) in S0 w/ workload 
- Compute fast charge times in S3