code: function patchForIOS (isEnd) {
    if (platform.needSpecialScroll && window !== window.top) {
      let element = document.createElement('div')
      element.style.cssText = isEnd
        ? 'position:absolute;width:0;height:0;visibility:hidden;'
        : 'position:absolute;top:0;left:0;width:0;height:0;visibility:hidden;'
      docBody.appendChild(element)
      return element
    }
    return null
  }
docs: When page in IOS-IFRAME, scroll and rect have some bugs.
  So we need add some elements to solve this problem.
  https://medium.com/@dvoytenko/amp-ios-scrolling-and-position-fixed-b854a5a0d451
  
  @inner
  @param {boolean} isEnd Create a ending element or not.
  @return {?HTMLElement}