The shared BrightnessLogic::BrightnessInfo struct had a membercalled valueBeforeTogglingOff, with some associated logic that'sonly used by its toggled() function.
ScreenBrightnessController never wanted anything to do with it,KeyboardBrightnessController already has a member to store the exactsame thing. Despite the "generic" API, KeyboardBrightnessControllerstill had to include a special case for toggling between off and on.
Putting this into shared infrastructure just makes everything morecomplicated than it should be, so let's make it local to the one ortwo functions where it actually gets used.