Avoid leaking documents in CustomElementRegistry's scoped document set #12092
Description
What is the issue with the HTML Standard?
As spec-ed the scoped document set holds a strong list of documents in the custom element registry. As far as I can tell, documents are never removed from this set so holding onto a CustomElementRegistry would leak documents (even if they had no relevant children to upgrade!).
e.g. In the following example, the created document leaks as long as registry lives:
const registry = new CustomElementRegistry();
const document = Document.parseHTMLUnsafe(`<!doctype html><x-foo></x-foo>`);
registry.initialize(document.querySelector("x-foo"));Given the only usage of the "scoped document set" is to upgrade relevant elements in a document whose custom element registry is already the registry we're calling .define on, can't we just hold a weak set of elements which need upgrading? (And simply build the set of documents during upgrade?).