Revert "Revert "frameworks: add SmartCover stubs""

This reverts commit 5160a95973365b92c82610a3e53ed355ef0c20e8.
Revert "Revert "Keyguard: add smart cover support""

This reverts commit c4233138f73362acfba333a993b93ace6c4704dd.
Revert "Revert "policy: respect FLAG_TURN_SCREEN_ON flag with device flip covers""

This reverts commit 6b9b76f9f865aa0c837abadf1357461228cf8dcf.