The emergency call button has been removed (since the user
can disable the keyguard, open the phone app, and enter the
emergency number there).
This change also restores a number of the informational &
help messages that were previously removed from the lock
screen.
Bug: 2421380
Change-Id: I4dda16be5d54c1e0ab4e26914c63d1f5b922cfe8