function delayForBusyIndicatorAndAssertIndicatorShown() {
  mockClock.tick(500);
  var element =
      goog.dom.getElementByClass('firebaseui-id-busy-indicator', container);
  assertNotNull(element);
}
Asserts that the busy indicator is shown after a short delay. The delay
exists so that pages that load quickly will not flash a loading bar.