[automerger skipped] DO NOT MERGE Add logging for when IOnBackInvokedCallback...

[automerger skipped] DO NOT MERGE Add logging for when IOnBackInvokedCallback is null. am: 30615002 am: 9eb1f83b -s ours am: 83fea0fb -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22442774



Change-Id: Id258a771718f0bc205cabd0fa649b10d75b87cab
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>