wayland: Only set newly_attached if the buffer changes

This cleans up the check to determine if the buffer changed,
meaning we shouldn't have to pass it around like we needed
to do before.

src/wayland/meta-wayland-surface.c

@@ -150,7 +150,7 @@ commit_attached_buffer (MetaWaylandSurface             *surface,
                         MetaWaylandDoubleBufferedState *pending)
 {
   /* wl_surface.attach */
-  if (pending->newly_attached && surface->buffer != pending->buffer)
+  if (pending->newly_attached)
     {
       surface_set_buffer (surface, pending->buffer);
       return TRUE;
@@ -416,6 +416,9 @@ wl_surface_attach (struct wl_client *client,
   else
     buffer = NULL;
 
+  if (surface->buffer == buffer)
+    return;
+
   if (surface->pending.buffer)
     wl_list_remove (&surface->pending.buffer_destroy_listener.link);