compositor: fix transformed opaque surface repainting

Computing the real maximal opaque screen aligned rectangle of a
transformed surface is hard. Let's drop the opaque optimisation
instead.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
diff --git a/src/compositor.c b/src/compositor.c
index bd5d2e7..a74ac30 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -474,7 +474,8 @@
 	weston_surface_damage(surface);
 
 	pixman_region32_fini(&surface->opaque);
-	if (surface->visual == WESTON_RGB_VISUAL)
+	if (surface->visual == WESTON_RGB_VISUAL &&
+	    surface->transform.enabled == 0)
 		pixman_region32_init_rect(&surface->opaque,
 					  surface->geometry.x,
 					  surface->geometry.y,