[automerger skipped] Merge "Hide start and cancel handover from api surface" am: ee4668c5a5 am: 42b6ecf0fc am: a57b0042fe -s ours

am skip reason: Change-Id I9e65ad178a843e92a59e5e4f7debd4d7b77a3edb with SHA-1 fa1cf3d5d8 is in history

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I5b884f65567d1863f72d72d1d1e9e317f9580c6f