Merge "Add a section about accessibility overlays at the top of AccessibilityService.java." into udc-dev am: 48df6022 am: 27fcfd63

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



Change-Id: I4e799a9219f58469a530c97ea0ffc112e7ae1dc5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>