function hideSelectPopup(mode = "enter", win = window) {
  let browser = win.gBrowser.selectedBrowser;
  let selectClosedPromise = SpecialPowers.spawn(browser, [], async function() {
    let { SelectContentHelper } = ChromeUtils.import(
      "resource://gre/actors/SelectChild.jsm"
    );
    return ContentTaskUtils.waitForCondition(() => !SelectContentHelper.open);
  });

  if (mode == "escape") {
    EventUtils.synthesizeKey("KEY_Escape", {}, win);
  } else if (mode == "enter") {
    EventUtils.synthesizeKey("KEY_Enter", {}, win);
  } else if (mode == "click") {
    let popup = win.document.getElementById("ContentSelectDropdown").menupopup;
    EventUtils.synthesizeMouseAtCenter(popup.lastElementChild, {}, win);
  }

  return selectClosedPromise;
}