[snapshot] optimizing WatchedArrayList snapshot am: d5c4c550 am: fb598827 am: d2649425 am: 44f3117f

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18185712



Change-Id: I3b194e23618ebf040896119dd1597d61893ed68e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>