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This implements the following:

1. New RenderFrameHost are put in their own new virtual browsing context
   group.
2. When a new window is created, the initial empty document inherits
   from its opener.
3. When a navigation happens, the virtual browsing context group is
   inherited from the previous document, except if the COOP/COEP/Origin
   states require a new virtual browsing context group to be used.

COOP access reporting:
[1/N] https://chromium-review.googlesource.com/c/chromium/src/+/2264294
[2/N] https://chromium-review.googlesource.com/c/chromium/src/+/2270185
[3/N] https://chromium-review.googlesource.com/c/chromium/src/+/2270472
[4/N] https://chromium-review.googlesource.com/c/chromium/src/+/2273120
[5/N] https://chromium-review.googlesource.com/c/chromium/src/+/2309433
[6/N] https://chromium-review.googlesource.com/c/chromium/src/+/2308715
[7/N] https://chromium-review.googlesource.com/c/chromium/src/+/2309697
[8/N] this patch.

Bug: 1090273
Change-Id: Ic9c2d5a17e222743c1f498ff30bb6564980bec27
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2275889
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Pâris Meuleman <pmeuleman@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790843}