invalid use of incomplete type 'class QWebFrame'

hi to all,
I've centos 6.6 and qt5.3.2 (x86). I am upgrading clipgrab-3.5.6 (qt4 ) to qt5 and having this problem :-

Code:

QString video_dailymotion::getQualityUrl(QString json, QString quality)
{
    QWebView* view = new QWebView();
    view->setHtml("<script>function data() {return " + json + ";}</script>");
    QString result = view->page()->mainFrame()->evaluateJavaScript("data().metadata.qualities['" + quality + "'][0].url").toString();
 
    view->deleteLater();
    return result;
}

error :-

Code:

/opt/software/clipgrab-3.5.6/video_dailymotion.cpp:120: error: invalid use of incomplete type 'class QWebFrame'
     result = view->page()->mainFrame()->evaluateJavaScript("data().metadata.qualities['" + quality + "'][0].url").toString();

how to solve this problem. why having this problem.