Reviewed by Andreas Kling.

        Remove null ptr deref that happens when reattaching to
        a new web process.

        Implement didRelaunchProcess that sets the drawing area size
        after the drawing area is re-instantiated.

        [Qt][WK2] Null ptr deref in UI process after web process has crashed
        https://bugs.webkit.org/show_bug.cgi?id=52796

        * UIProcess/API/qt/qgraphicswkview.cpp:
        (QGraphicsWKView::QGraphicsWKView):
        * UIProcess/API/qt/qwkpage.cpp:
        (QWKPagePrivate::QWKPagePrivate):
        (QWKPagePrivate::init):
        (QWKPagePrivate::createDrawingAreaProxy):
        (QWKPagePrivate::didRelaunchProcess): Reset drawing area size after crash.
        * UIProcess/API/qt/qwkpage_p.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76262 268f45cc-cd09-0410-ab3c-d52691b4dbfc