testHighlightFirstOnOpen_withEnterOrSpaceSet() {
    const node = dom.getElement('demoMenuButton');
    menuButton.decorate(node);
    menuButton.setSelectFirstOnEnterOrSpace(true);
    menuButton.handleKeyEvent(new MyFakeEvent(KeyCodes.ENTER));
    assertEquals(
        'The first item should be highlighted when opened with enter ' +
            'after setting selectFirstOnEnterOrSpace',
        'menuItem1', menuButton.getMenu().getHighlighted().getElement().id);
  }
Check that the appropriate items are selected when menus are opened with
the keyboard and setSelectFirstOnEnterOrSpace is set.
@suppress {checkTypes} suppression added to enable type checking