function toggleCssProps(manager, add) {
  let { element } = manager;
  if (!element.style) {
    return;
  }
  let prop;
  each(manager.options.cssProps, (value, name) => {
    prop = prefixed(element.style, name);
    if (add) {
      manager.oldCssProps[prop] = element.style[prop];
      element.style[prop] = value;
    } else {
      element.style[prop] = manager.oldCssProps[prop] || '';
    }
  });
  if (!add) {
    manager.oldCssProps = {};
  }
}
@private
add/remove the css properties as defined in manager.options.cssProps
@param {Manager} manager
@param {Boolean} add