Merge "Add dark scrim from a background thread during unfold" into tm-qpr-dev am: d1783ae8

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20437905



Change-Id: I62f7445194c5031f17c764c9d8baff3fde47865a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>