message: Better focus behaviour on menu close
  If they click the backdrop, give focus to the rustdoc container,
  and otherwise give the focus to the menu button itself.
diff: return allItems[allItems.length - 1];
  }
  function closeMenu() {
  + if (this === backdrop) {
  + var rustdoc = document.querySelector(".rustdoc");
  + if (rustdoc) {
  + rustdoc.focus();
  + } else {
  + document.documentElement.focus();
  + }
  + } else if (currentMenu.querySelector(".pure-menu-link:focus")) {
  + currentMenu.firstElementChild.focus();
  + }
  currentMenu.className = currentMenu.className.replace("pure-menu-active", "");
  currentMenu = null;
  backdrop.style.display = "none";
  // but is a rationalization of GitHub's behavior: we don't want users who know how to
  // use tab and enter, but don't know that they can close menus with Escape,
  // to find themselves completely trapped in the menu
  - currentMenu.firstElementChild.focus();
  closeMenu();
  e.preventDefault();
  e.stopPropagation();
  