There already exists adjustable, default values in the java layer for this stuff so
we will leverage that instead.
Test: Ensure that going into VR mode still sets the value to correct
default.
Bug: 73090564
Change-Id: Id9929f074219fee74f93def5227e92ea9b6f55a0
Bug : 62663757
If sys.display.low_persistence_mode_brightness is set, get brightness
from sys.display.low_persistence_mode_brightness.
Change-Id: I21a7583f535f8797300bab738cc4c8805ca06b90
The file /sys/class/leds/button-backlight/brightness isn't
created/exposed by the kernel.
Bug: 36097008
Test: LightHidlTest.TestSupported now passes.
Change-Id: If2e036cfa9fdb36596bc0820480072fde7591112