Merge "Inject back key events if no focus window found." into tm-qpr-dev am: 117bab59

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19144840



Change-Id: Ifcb3e44f8ccf21dde71a7663058380a0ca117aa4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>