[automerger skipped] DO NOT MERGE Handle back button for notification panel am: 2f5e1b40 am: 5d7be49d -s ours

am skip reason: subject contains skip directive

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I248f8da2e706cc72636a91a6e3e71050fee58efa