Added safeguards for pushed brighntess curve.

Currently, the only safeguard is making sure the brightness curve isn't too dark to turn
auto-brightness off (or connect the phone to a computer and reset the curve with ADB).

Test: atest BrightnessMappingStrategyTest.

Change-Id: Ic87292fe51639a0001d0d5643ca24cda37de5753
Fixes: 74439069
4 files changed