[gtk+] Add a transfer annotation

[Matthias Clasen <matthiasc src gnome org>]

commit e71f7d713e652ed0db4828b9c3e841766073922c
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Dec 28 14:41:33 2015 -0500

    Add a transfer annotation
    
    This was confusing me momentarily, so add an explicit annotation.

 gtk/gtkcssstyleproperty.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkcssstyleproperty.c b/gtk/gtkcssstyleproperty.c
index 6cf0ccf..e4d3f8f 100644
--- a/gtk/gtkcssstyleproperty.c
+++ b/gtk/gtkcssstyleproperty.c
@@ -385,7 +385,7 @@ _gtk_css_style_property_get_id (GtkCssStyleProperty *property)
  * [CSS Documentation](http://www.w3.org/TR/css3-cascade/#intial)
  * for an explanation of this concept.
  *
- * Returns: a reference to the initial value. The value will never change.
+ * Returns: (transfer none): the initial value. The value will never change.
  **/
 GtkCssValue *
 _gtk_css_style_property_get_initial_value (GtkCssStyleProperty *property)