Stop worrying about tiny OOMs. Work towards #20449. While going through these, I also changed the function signature in many places where returning ThrowCompletionOr<T> is no longer necessary.
This class is currently not in the spec, but it *is* still in all the major browser engines. For compatibility reasons, let's do what other engines do. There is discussion about bringing HTMLDocument back into specs: - https://github.com/whatwg/html/issues/4792 - https://github.com/whatwg/dom/issues/221