... when generalizing const fields to mutable fields.

Bug: chromium:748539, chromium:747979, chromium:738763
Change-Id: Iee772a5d0cddd23599f1f68bca00b8beecb76da0
Reviewed-on: https://chromium-review.googlesource.com/586709Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46921}