Remove pizza backing window.

When it is present, no-window widgets sometimes don't get expose events for
reasons I could not determine. And it is dubious that it improved scrolling
performance on modern hardware anyway, and almost certainly doesn't help now
that GTK+ is using "client side windows".


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64431 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/window.cpp

@@ -4388,7 +4388,7 @@ GdkWindow* wxWindowGTK::GTKGetDrawingWindow() const
 {
     GdkWindow* window = NULL;
     if (m_wxwindow)
-        window = WX_PIZZA(m_wxwindow)->m_draw_window;
+        window = m_wxwindow->window;
     return window;
 }