GitLab

With SlimNavigationManager enabled, navigating back to a restore URL after a
cold launch DCHECKs because the webUI is not cleared.

Bug: 996221
Change-Id: I2c754f2e95dd6fad3cb7861eaff275602154671d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1773700Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691815}