Merge "Only allow trusted overlays to specify FLAG_SLIPPERY" into sc-dev am: 94fb6eff68 am: 34798dcab0

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15748730

Change-Id: I25f7c05f9d68050f2cacfe5e92196db83d5bc8da