[DO NOT MERGE] Update window with FLAG_SECURE when bouncer is showing

This will prevent bouncer interactions from showing up in
screenrecords or screenshots.

Fixes: 215005011
Test: atest NotificationShadeWindowControllerImpl && take screenshot
with bouncer up

Change-Id: I3f59df865dc2dd13d4b9ac54bb2dacb7b23f0aa1
Merged-In: I3f59df865dc2dd13d4b9ac54bb2dacb7b23f0aa1
(cherry picked from commit 6888543d)