[automerger skipped] [RESTRICT AUTOMERGE] Add hide-non-system-overlay flag for HarmfulAppWarningActivity am: 9c5c42ad03 am: 655a7e98de -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16743243

Change-Id: Idd369b8cdd3e0b2a6c1c7197094d8fe231c25b70