[DO NOT MERGE] Update window with FLAG_SECURE when bouncer is showing am: bc2146966b

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19952038

Change-Id: I18ee62f32bf7c7364ad5e88643a6cd3ac7f8eb71
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>