compositor: Remove special casing of fullscreen surfaces

This was supposed to draw black borders around a fullscreen surface that
was smaller than the output.  We don't want to special case that in the
repaint loop, but may use a different shader or such.  And we want the
surface to have an opaque region that covers the output so that that
will eliminate overdraw of lower surfaces.

src/compositor.c

@@ -833,15 +833,8 @@ weston_output_repaint(struct weston_output *output)
 		/* We're drawing nothing, just let the damage accumulate */
 		return;
 
-	if (es->fullscreen_output == output) {
-		if (es->width < output->current->width ||
-		    es->height < output->current->height)
-			glClear(GL_COLOR_BUFFER_BIT);
-		weston_surface_draw(es, output);
-	} else {
 	wl_list_for_each_reverse(es, &ec->surface_list, link)
 		weston_surface_draw(es, output);
-	}
 
 	if (ec->fade.spring.current > 0.001)
 		fade_output(output, ec->fade.spring.current, &total_damage);