Merge "Add additional javadoc for VcnManager" am: ba3f1179a8 am: e1a23d3245

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1458805

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I7fd09281181e62a3f01171484d57512d71e48c1f