To reproduce, after setting GOBJECT_DEBUG=objects, run gtk3-icon-browser,
click n times on the same icon in the icon-view and close n times
the dialog showing icon details.

In the output there are 5 stale pixbufs with a ref_count > n.

Repeating the test doubling n, the ref_count increases of
n.

The problem is here:

https://git.gnome.org/browse/gtk+/tree/demos/icon-browser/iconbrowserwin.c?h=gtk-3-22#n84

gtk_drag_source_set_icon_pixbuf

https://git.gnome.org/browse/gtk+/tree/gtk/gtkdragsource.c?h=gtk-3-22#n364

references the pixbuf and then calls gtk_image_definition_new_pixbuf
which adds its own reference to the pixbuf, reference removed when
gtk_image_definition_unref is called.



I think that the g_object_ref is a leftover since this commit:

https://git.gnome.org/browse/gtk+/commit/gtk/gtkdnd.c?h=gtk-3-22&id=adbfbb72783dccaeac773a8878e66d2300996f1e

The g_object_ref is now part of gtk_image_definition_new_pixbuf
and if there is the possibility that pixuf is the same as the one
stored in site->image_def with only one reference, then it is      
necessary to add a g_object_unref at the end of the function.