[Qt][WK2] Replace more uses of WebPageProxy with WKPage in QQuickWebView
https://bugs.webkit.org/show_bug.cgi?id=108826

Reviewed by Kenneth Rohde Christiansen and signed off for WK2 by
Benjamin Poulain.

This patch converts a few more usages of WebPageProxy to functions in
the WKPage API.

* UIProcess/API/qt/qquickwebview.cpp:
(QQuickWebViewPrivate::initialize):
(QQuickWebViewLegacyPrivate::zoomFactor):
(QQuickWebViewLegacyPrivate::setZoomFactor):
(QQuickWebViewExperimental::postMessage):
(QQuickWebViewExperimental::userAgent):
(QQuickWebViewExperimental::setUserAgent):
(QQuickWebViewExperimental::evaluateJavaScript):
(QQuickWebViewExperimental::findText):
(QQuickWebView::goBack):
(QQuickWebView::goForward):
(QQuickWebView::stop):
(QQuickWebView::reload):
(QQuickWebView::setUrl):
(QQuickWebView::canGoBack):
(QQuickWebView::canGoForward):
(QQuickWebView::loading):
(QQuickWebView::title):
(QQuickWebView::pageRef):
(QQuickWebView::loadHtml):
(QQuickWebView::runJavaScriptInMainFrame):
* UIProcess/API/qt/qquickwebview_p_p.h:
(QQuickWebViewPrivate):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141882 268f45cc-cd09-0410-ab3c-d52691b4dbfc