GitLab

This CL makes sure that the correct URL (i.e. the one of the page that
created the error) is used instead of the error page file URL.

To do this, this CL uses IsLoadingErrorPage with the new error page
workflow. It allows to have the URL of the loaded page (not the URL of
the error page) and having the navigation marked as being a navigation
to an error page. Then the callbacks can act on it.

The main difference with the non-JS workflow is the back-forward
navigation. Because the URL of the page is the URL of the file page
that is displaying the error, we need to mark the navigation as a
error page navigation.
Then the navigation to the real page starts, and it is a new context
so it is no longer an error page navigation.

Bug: 991608
Change-Id: I4362d1cc50262ea86db1e211bfaec619f008625e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2449391Reviewed-by: Ali Juma <ajuma@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815177}