Merge "Annotation and doc improvement for adhoc conference APIs." am: 0251d617a5 am: e4bc4e9ca5

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1412812

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Iee57bef7f60bb612b864a72d5bf2d98115b03d28