Allowing cross-origin isolation with Oauth popups.

Hi everyone,

In recent years, browsers have gated some Web APIs behind
crossOriginIsolated
<https://developer.mozilla.org/en-US/docs/Web/API/crossOriginIsolated>, see
https://web.dev/coop-coep/ for more details. One of the pain points of
deploying Cross-Origin-Opener-Policy (COOP), which is one of the
requirements, is that it prevents working with third-party Oauth providers
in the form of popups.

We've thought about a possible solution in this github thread:
https://github.com/whatwg/html/issues/6364, which led to this explainer:
https://github.com/hemeryar/explainers/blob/main/coop_restrict_properties.md

We'd be very interested to know if that solution would be suitable for you!

Cheers,
Arthur H. from the Chrome web platform security team.