GitLab

The [coop-reporting-explainer] defined several URLs that might be
reported:
- openeeURL
- openerURL
- otherDocumentURL
- referrerURL
- initialPopupURL

This adds the first 3.

[coop-reporting-explainer]:
https://github.com/camillelamy/explainers/blob/master/coop_reporting.md

Bug: 1090273
Change-Id: Ibd9710139e0065bd36fe6e798b50521f6d24baf6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398619
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812144}