function assertResendCountdown(timeRemaining) {
  var el =
      goog.dom.getElementByClass('firebaseui-id-resend-countdown', container);
  var expected = firebaseui.auth.soy2.strings
                 .resendCountdown({timeRemaining: timeRemaining})
                 .toString();
  var actual = goog.dom.getTextContent(el);
  assertEquals(expected, actual);
}
Asserts the resend countdown indicates the given time remaining.
@param {number} timeRemaining The time remaining.