function checkAriaState(button) {
  assertEquals(
      'menu buttons should have default aria-expanded == false', 'false',
      aria.getState(button.getElement(), State.EXPANDED));
  button.setOpen(true);
  assertEquals(
      'menu buttons should not aria-expanded == true after ' +
          'opening',
      'true', aria.getState(button.getElement(), State.EXPANDED));
}
Verify that the menu button has the correct ARIA attributes
@param {?Button} button A button.
@suppress {checkTypes} suppression added to enable type checking