Only allow trusted overlays to specify FLAG_SLIPPERY

For all other requests, drop this flag.

Test: atest FlagSlipperyTest
Bug: 157929241
Change-Id: Ia30f1c38d5ddb351c90b748ea76448a76a9dde7b
Merged-In: Ia30f1c38d5ddb351c90b748ea76448a76a9dde7b
2 files changed