Per spec [1], we should copy over the complete document state [2], which includes the referrer info. Bug 1773192 has already added this for the "replace" case when the session history is in parent (almost always the case), but it is still missing for the "push" case, and the "replace" case when the session history is not in parent. [1] https://html.spec.whatwg.org/multipage/browsing-the-web.html#url-and-history-update-steps [2] https://html.spec.whatwg.org/multipage/browsing-the-web.html#document-state Differential Revision: https://phabricator.services.mozilla.com/D200684
