[gtk/matthiasc/for-master] gtk-demo: Add the shader paintable sources

[Matthias Clasen <matthiasc src gnome org>]

commit 72eb89eda709bd728816902628add72980340fc9
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Sep 30 15:41:05 2020 -0400

    gtk-demo: Add the shader paintable sources
    
    This is currently not public GTK api, just part of
    the demo. So we should show it here.

 demos/gtk-demo/demo.gresource.xml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/demos/gtk-demo/demo.gresource.xml b/demos/gtk-demo/demo.gresource.xml
index 2b7cdc0a8a..224b4736e2 100644
--- a/demos/gtk-demo/demo.gresource.xml
+++ b/demos/gtk-demo/demo.gresource.xml
@@ -138,6 +138,8 @@
     <file>gtkshaderstack.h</file>
     <file>gtkshaderbin.h</file>
     <file>gtkshaderbin.c</file>
+    <file>gskshaderpaintable.h</file>
+    <file>gskshaderpaintable.c</file>
     <file>ripple.glsl</file>
     <file>background.glsl</file>
    <file>transition1.glsl</file>