[automerger skipped] [RESTRICT AUTOMERGE] Add hide-non-system-overlay flag for HarmfulAppWarningActivity am: 2c87a8a7 am: a04ffe43 -s ours am: d5fed4ae -s ours

am skip reason: subject contains skip directive

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

Change-Id: I8526a4ba7da4bedadbd7bda38f4230517ab7deec