Do not access web state while the CRWWebController is being destroyed.

Bug: 935555
Change-Id: I3ace36ecc6ec84205b90edb57de6c2c993201bec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1489713
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639194}
13 files changed