Merge "Expose adhoc conference calling API as public." am: 8ebbe3c038 am: fb8f41f0c2 am: e8a4750ac5

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1368819

Change-Id: I9c47ae98bd0a1d5e529a2d59c0fd1657ae061a53