Avoid updating class loaders outside system weaks am: f3c44b4109 am: e2a6a647a1 am: 5a2596e3dc

Original change: https://android-review.googlesource.com/c/platform/art/+/2242213

Change-Id: I868547864e2faaf3d79a04fc232e07cc9a3f9858
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>