[gtk+] cssimage: Don't start a transition if the start and end are the same

[Jasper St. Pierre <jstpierre src gnome org>]

commit ce75c835e1710c9c6db4fa9d45ca96a4faafa85f
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sun Aug 2 12:35:45 2015 -0700

    cssimage: Don't start a transition if the start and end are the same
    
    Since a lot of Adwaita sets transition: all, it's easy to end up in a
    state where we're making dummy transitions for all of the icons, most of
    which we'll never be showing.

 gtk/gtkcssimage.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcssimage.c b/gtk/gtkcssimage.c
index 2d92829..31b1e80 100644
--- a/gtk/gtkcssimage.c
+++ b/gtk/gtkcssimage.c
@@ -87,6 +87,8 @@ gtk_css_image_real_transition (GtkCssImage *start,
     return g_object_ref (start);
   else if (progress >= 1.0)
     return end ? g_object_ref (end) : NULL;
+  else if (_gtk_css_image_equal (start, end))
+    return g_object_ref (start);
   else
     return _gtk_css_image_cross_fade_new (start, end, progress);
 }