This should make uses of the type more clearly indicating where the origin came from, and should help avoid potential confusion between this origin and nsIPrincipal::origin in new code. This new name is long, but explicit. The string returned from this function corresponds to the "serialization of an origin" from the WHATWG html spec: https://html.spec.whatwg.org/multipage/browsers.html#ascii-serialisation-of-an-origin Differential Revision: https://phabricator.services.mozilla.com/D181794
