"Append mo to unit of related similar-origin bro..." #720
Description
Append mo to unit of related similar-origin browsing contexts' mutation observer list.
If my understanding is correct, this should be held as a weak pointer, not the traditional strong pointer. Otherwise, MutationObserver objects can never be garbage collected.
This probably deserves at least a note in the spec. Or, you could change the list to "weak set", as is done for https://html.spec.whatwg.org/multipage/webappapis.html#outstanding-rejected-promises-weak-set . Or we could start formalizing this concept of reference graphs in Infra.