d159f1178c
This wasn't done consistently (otherwise bug 1936194 wouldn't have worked). Now that we recreate the popups when needed, we can rely on that instead of reparenting the widget. Popups are the only type of widget we should ever reparent, as other widgets are created at the top level which can't be moved around. Differential Revision: https://phabricator.services.mozilla.com/D232202