Merge "Add explanation about the purpose of accessibility heading and use case...

Merge "Add explanation about the purpose of accessibility heading and use case apps should consider." am: 407d5317 am: afc1b7d0 am: 08ae6de0 am: 389bce37

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2151635



Change-Id: Ife6f292b0350a51409ed45d075a379890ada7b8b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>