GitLab

This CL revives some of the checks from r512959 to ensure that most
extension URLs only commit in the correct extension processes.
There are several exceptions that must be accounted for.

BUG=770239, 840857

Change-Id: Id3dd2a7814041186d4de6f61e2dee440939b57d9
Reviewed-on: https://chromium-review.googlesource.com/1025075
Commit-Queue: Charlie Reis <creis@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567799}