Merge "Annotation and doc improvement for adhoc conference APIs." am: 0251d617a5 am: e4bc4e9ca5 am: 3e96c1328c

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ie849bba0805a1a43a841ae204337c12d3f5d9791