st-shadow: Add a CoglFramebuffer argument

The last patch in the series, this one adapts StShadowHelper
to received a CoglFramebuffer. This is where we first touch
JavaScript with Cogl types, and as such, it depends on the
latest Mutter. Earlier versions of Mutter didn't have its
Mutter-Clutter GIR to generate types for various Cogl types.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/283

src/st/st-shadow.c

@@ -276,6 +276,7 @@ st_shadow_helper_free (StShadowHelper *helper)
 /**
  * st_shadow_helper_paint:
  * @helper: a #StShadowHelper
+ * @framebuffer: a #CoglFramebuffer
  * @actor_box: the bounding box of the shadow
  * @paint_opacity: the opacity at which the shadow is painted
  *
@@ -284,11 +285,12 @@ st_shadow_helper_free (StShadowHelper *helper)
  */
 void
 st_shadow_helper_paint (StShadowHelper  *helper,
+                        CoglFramebuffer *framebuffer,
                         ClutterActorBox *actor_box,
                         guint8           paint_opacity)
 {
   _st_paint_shadow_with_opacity (helper->shadow,
-                                 cogl_get_draw_framebuffer (),
+                                 framebuffer,
                                  helper->pipeline,
                                  actor_box,
                                  paint_opacity);

src/st/st-shadow.h

@@ -84,6 +84,7 @@ void            st_shadow_helper_update (StShadowHelper *helper,
                                          ClutterActor   *source);
 
 void            st_shadow_helper_paint (StShadowHelper  *helper,
+                                        CoglFramebuffer *framebuffer,
                                         ClutterActorBox *actor_box,
                                         guint8           paint_opacity);