Reviewed by Sam Weinig.

        When resizing, the web process should repaint the page
        https://bugs.webkit.org/show_bug.cgi?id=52764

        * UIProcess/DrawingAreaProxyImpl.cpp:
        (WebKit::DrawingAreaProxyImpl::didSetSize):
        Incorporate the update.

        (WebKit::DrawingAreaProxyImpl::incorporateUpdate):
        Return early if the update bounds rect is empty. This can happen if painting is
        disabled and we get a DidSetSize message.

        * WebProcess/WebPage/DrawingAreaImpl.cpp:
        (WebKit::DrawingAreaImpl::setSize):
        If painting is disabled, just send back an empty UpdateInfo struct. Otherwise,
        paint and fill in the UpdateInfo struct.

        (WebKit::DrawingAreaImpl::display):
        Assert that painting is not disabled.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76179 268f45cc-cd09-0410-ab3c-d52691b4dbfc