Proper battery paths

* 4.4 introduces a new daemon, healthd, that handles battery status
    - resides in: /system/core/healthd
    - BatteryMonitor.cpp iterates through all the *directories* under
      /sys/class/power_supply looking for a file called 'type'
    - if the type == Battery, it assumes this is the location for the
      battery stats for the device. Only the first directory that matches
      this criteria is used.
    - on msm8660/d2/jf/s2 kernels, this search results in:
      /sys/class/power_supply/fuelgauge.
    - To determine capacity, healthd looks at the contents of the
      'capacity' file under this discovered base path. This results
      in /sys/class/power_supply/fuelgauge/capacity on msm8660/d2/jf/s2
      kernels.
    - Unfortunately, this is the wrong path. The capacity file at this
      location returns a large negative number.
    - Other paths like status, voltage_now, and present are also
      incorrectly determined.
  * For comparison, in 4.3 battery statistics gathering was handled by
    frameworks/base/services/jni/com_android_server_BatteryService.cpp
    - BatteryService does a similar search for a file called 'type' with
      the contents of 'Battery'
    - But the search logic is different here: it takes the *last* path that
      matches the criteria.
    - This results in the correct /sys/class/power_supply/battery
  * This patch overrides the discovery mechanism for battery status completely.

Change-Id: I4579c92bba5596eef4dac67b8c0687be50a1d2f5
3 files changed