compositor: Do not optimize obscured areas away in paint volumes

This optimization was presumably added before Clutter was able to
invalidate selected regions of an actor. Paint volumes are supposed
to be invariable as long as the actor conditions don't change.
Stacking of other actors shouldn't affect the paint volume, so it's
actually wrong to optimize those areas away here.

src/compositor/meta-shaped-texture.c

@@ -694,46 +694,11 @@ effective_unobscured_region (MetaShapedTexture *self)
   return priv->unobscured_region;
 }
 
-static gboolean
-get_unobscured_bounds (MetaShapedTexture     *self,
-                       cairo_rectangle_int_t *unobscured_bounds)
-{
-  cairo_region_t *unobscured_region = effective_unobscured_region (self);
-
-  if (unobscured_region)
-    {
-      cairo_region_get_extents (unobscured_region, unobscured_bounds);
-      return TRUE;
-    }
-  else
-    return FALSE;
-}
-
 static gboolean
 meta_shaped_texture_get_paint_volume (ClutterActor *actor,
                                       ClutterPaintVolume *volume)
 {
-  MetaShapedTexture *self = META_SHAPED_TEXTURE (actor);
+  return clutter_paint_volume_set_from_allocation (volume, actor);
-  ClutterActorBox box;
-  cairo_rectangle_int_t unobscured_bounds;
-
-  if (!clutter_actor_has_allocation (actor))
-    return FALSE;
-
-  clutter_actor_get_allocation_box (actor, &box);
-
-  if (get_unobscured_bounds (self, &unobscured_bounds))
-    {
-      box.x1 = MAX (unobscured_bounds.x, box.x1);
-      box.x2 = MIN (unobscured_bounds.x + unobscured_bounds.width, box.x2);
-      box.y1 = MAX (unobscured_bounds.y, box.y1);
-      box.y2 = MIN (unobscured_bounds.y + unobscured_bounds.height, box.y2);
-    }
-  box.x2 = MAX (box.x2, box.x1);
-  box.y2 = MAX (box.y2, box.y1);
-
-  clutter_paint_volume_union_box (volume, &box);
-  return TRUE;
 }
 
 void