Make graph delegate visitor classes final. am: bb04c9d87b am: c56e5c60e9

Original change: https://android-review.googlesource.com/c/platform/art/+/2969622

Change-Id: I3817cb777ac0ece35e59e206e1eabd929a3c15e0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>