Merge "Add a section about accessibility overlays at the top of...

Merge "Add a section about accessibility overlays at the top of AccessibilityService.java." into udc-dev am: 48df6022

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21586660



Change-Id: I23113fffbd3b6b52dd7e3536c7b6ee03d2424268
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>