Add the surface context to the Surface's setParent

In order to set the private context variable so that initiSurface can use it.

src/apprt/gtk/class/surface.zig

@@ -699,6 +699,7 @@ pub const Surface = extern struct {
     pub fn setParent(
         self: *Self,
         parent: *CoreSurface,
+        context: apprt.surface.NewSurfaceContext,
     ) void {
         const priv = self.private();
 
@@ -709,6 +710,9 @@ pub const Surface = extern struct {
             return;
         }
 
+        // Store the context so initSurface can use it
+        priv.context = context;
+
         // Setup our font size
         const font_size_ptr = glib.ext.create(font.face.DesiredSize);
         errdefer glib.ext.destroy(font_size_ptr);