From the commit message:
Switch to render nodes. Most of the changes follow the pattern of replacing a cogl_framebuffer_draw_*() call by (1) creating a paint node, and (2) calling the corresponding clutter_paint_node_add_*() API. StWidget now overrides ClutterActor.paint_node(), instead of paint. All subclasses that overrided the paint vfunc also are changed to override paint_node. The entry point for CSS rendering, st_widget_paint_background(), now receives a root ClutterPaintNode, and propagates it to the rendering machinery.
Depends on mutter!1637 (merged)