Specify behavior for non-fully active documents

[mreichhoff]

Please see discussion in https://crbug.com/1354256 for context. The particular case that started this discussion was behavior in detached frames. The wording was largely pulled from: https://github.com/whatwg/webidl/blob/main/index.bs#L8510-L8511

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[mreichhoff]

@johannhof @domfarolino

would you be willing to take a look? Feedback is welcome.

Thanks!

[mreichhoff]

good call...all the other ones use wording like: resolve |p| with false and return |p|, which matches the domfarolino suggestion. I used that instead.

Let me know of anything else. Thanks!

[johannhof]

Thanks!