GitLab

This has two side effects:
* We no longer need to check that a navigation is in the main frame,
  but I did leave a DCHECK there anyways.
* The temp hack for ORIGINAL_REQUEST_URL is removed.

Bug: 898557, 864646
Change-Id: Ib767fd0b2e8d7675cf1b6e5ae7a4eec282378680
Reviewed-on: https://chromium-review.googlesource.com/c/1344551Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609913}