Merge "Remove BackPanelController#staysHiddenBeforeSlopCrossed" into tm-qpr-dev am: 0f139ec646 am: 4493ae5993

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21299080

Change-Id: I58284dceb4de2a4f7aa29f9bea363d86d8c69c78
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>