This introduces a boolean flag in which when set to true, Wallpaper
Attribution will be shown in the Legal page. When set to false, it
will be hidden. Wallpaper has always been removed from search results,
so that has not changed.
Bug: 62378616
Test: make RunSettingsRoboTests ROBOTEST_FILTER=LegalSettings passes.
Change-Id: Ia6f3e7d1ef471eecf79f1b46616fa4ba27d35748
Bug: 30681771
Test: SettingsUnitTests
Refactor visibility logging from InstrumentedFragment into a mixin. And
apply mixin in remaining fragments.
Change-Id: Ibbb59904336254a3e4bb9e8c7d0b36e5a6bc2622