Clean up BatteryMeterDrawable internal api.

Bug: 32539932
Test: runtest -x frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/graph/BatteryMeterDrawableBaseTest.java
Test: runtest -x frameworks/base/packages/SystemUI/tests/src/com/android/systemui/BatteryMeterDrawableTest.java
Change-Id: Ifdc3368b930abcf248b60ee99f6f9139ad804f91
6 files changed