Merge "Adds start/end button unfold transitions." into tm-qpr-dev am: 5685efd6 am: 2608fbad

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19531009



Change-Id: Ie8a06f8744e8e1f6c8da24657e041769b6e2cddb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>