[dom] _Which_ unit of related similar-origin browsing contexts?

domenic has just created a new issue for =

https://github.com/whatwg/dom:

=3D=3D _Which_ unit of related similar-origin browsing contexts? =3D=3D
Mutation observer algorithm steps say:

> Let notify list be a copy of unit of related similar-origin browsing
 contexts' list of MutationObserver objects. =


and

> append it to the unit of related similar-origin browsing contexts' =

list of MutationObserver objects, and then return it.

This seems pretty ambiguous to me. Shouldn't be trying to go from e.g.
 entry settings object to browsing context to unit of related =

similar-origin browsing contexts, or something?

Maybe HTML needs to define "current unit of related similar-origin =

browsing contexts"?

See https://github.com/whatwg/dom/issues/88