[automerger skipped] [RESTRICT AUTOMERGE] Add hide-non-system-overlay flag for HarmfulAppWarningActivity am: 2c87a8a7ce am: a04ffe4326 -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16743363

Change-Id: I169a506597dcc765e89cd224facedab1c16dbf75