Merge "Prevent callback registration when back flag is disabled" into tm-dev...

Merge "Prevent callback registration when back flag is disabled" into tm-dev am: 1c6de844 am: 0592820f am: f238735a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18794217



Change-Id: I5997a2878a4ab0e6f31dab5f20a9fd2513a53b40
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>