Merge "Introduce a flag for new back affordance" into tm-qpr-dev am: 593ac556

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18917212



Change-Id: I5fbf44fa30eb94f506cf6d55e97b79d414172dc9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>