[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

Merged-In: I3f59df865dc2dd13d4b9ac54bb2dacb7b23f0aa1
Change-Id: Icde7849a181ce8e0c1074537f6dde897aedd8bb3