Make user deletion dialog reusable.

This change will be immediately integrated into master.

This dialog will be also used by the alternate lock screen.

Bug: 25192625
Change-Id: Idc374312fe884af104e342d58f207e0510b9754a
(cherry picked from commit b29374806c393a06c993e5c6b92c62f06d5978c7)
3 files changed