[gegl] GeglNode: Short circuit gegl_node_set_passthrough if the value is same

[Debarshi Ray <debarshir src gnome org>]

commit c40abe78e8c5501e03afd4d4b50285f92cc2f574
Author: Debarshi Ray <debarshir gnome org>
Date:   Fri Apr 8 17:05:10 2016 +0200

    GeglNode: Short circuit gegl_node_set_passthrough if the value is same
    
    https://bugzilla.gnome.org/show_bug.cgi?id=764795

 gegl/graph/gegl-node.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gegl/graph/gegl-node.c b/gegl/graph/gegl-node.c
index e9747aa..ecd3e2c 100644
--- a/gegl/graph/gegl-node.c
+++ b/gegl/graph/gegl-node.c
@@ -2164,6 +2164,9 @@ gegl_node_set_passthrough (GeglNode *node,
 {
   g_return_if_fail (GEGL_IS_NODE (node));
 
+  if (node->passthrough == passthrough)
+    return;
+
   gegl_node_invalidated (node, NULL, TRUE);
   node->passthrough = passthrough;
 }