DocumentComplete的文档接近尾声的事件提及:Intheloadingprocess,thehighestlevelframe,whichisnotnecessarilythetop-levelframe,firesthefinalDWebBrowserEvents2::DocumentCompleteevent.Atthistime,thepDispparameteristhesameastheIDispatchinterfacepointerofthehighestlevelframe.最高层框架和顶级框架有什么区别,如何获取对最高层框架的引用?