[automerger skipped] DO NOT MERGE Handle back button for notification panel am: 2f5e1b40 am: 5d7be49d -s ours am: c7299367 am: 1b13a8f0 -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: I535d3624e084d340685975e5f784dceb8c7f3104