code: function(e) {
        if (location.href != prevHref) return;
        wrapper.removeChild(iframe);
        document.title = prevTitle;
        body.removeChild(wrapper);
        body.setAttribute('style',
          body.getAttribute('style').replace('overflow: hidden;', ''));
        removeEventListener('popstate', onPopState);
      }
docs: On back-button remove the wrapper