[automerger skipped] [RESTRICT AUTOMERGE] Add hide-non-system-overlay flag for HarmfulAppWarningActivity am: 53ee9c2472 am: be7090b09e -s ours am: b0cb54d596 -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16743244

Change-Id: Iba705847fda2c50a435113e9dad9554f559eb270