Merge "DO NOT MERGE Handle back button for notification panel" into rvc-qpr-dev am: 7d4b625cb2

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/13408029

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I7085fce31c5e2a8540e0bad63832068f3d6cdf65