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This sets a popup to noopener when:
  - COOP is same-origin,
  - a cross-origin iframe opens the popup.

As specified in the draft:
  https://gist.github.com/annevk/6f2dd8c79c77123f39797f6bdac43f3e#changes-to-choosing-a-browsing-context

Bug: 922191
Change-Id: Ie3aade8087b487998e7144375640f2e9a838a23f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1980173Reviewed-by: Arthur Hemery <ahemery@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Auto-Submit: Pâris Meuleman <pmeuleman@chromium.org>
Commit-Queue: Arthur Hemery <ahemery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728164}