Merge "Hide start and cancel handover from api surface" am: ee4668c5a5 am: 42b6ecf0fc

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1598495

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I8a4de2f0aae42da567e997982cc655759f88d0f1