Instead of toggled on being to keep battery saver on, the UX writers would like to make toggled on be turn battery saver off automatically. Also turns the controller into a TogglePreferenceController, because those exist apparently. Test: visual inspection, tests pass Fixes: 126938839 Change-Id: Iffac536d0b1956d4534ca1b5fa5c6440c4d3a3ff