QWebView::setZoomFactor does not work on Symban^3

QWebView：：setZoomFactor works well on my desktop, but it does not work on N8 and E7.

I used following test code:
mWebView = new QWebView(this);
mWebView->load(QUrl("http://www.baidu.com"));
mWebView->setGeometry(0, 100, 360 ,540);
mWebView->setZoomFactor(2);
mWebView->show();