GtkCellRendererPixbuf: Set force_scale_pixbuf

The recent icon theme scaling changes make the code more
sensitive to mis-sized icons (e.g. application icons in
the app chooser). A single row whose size gets blown out
of proportion by a big icon is never wanted in a list.
We can avoid this situation by telling GtkIconHelper to
force-scale the pixbuf to the requested size.

gtk/gtkcellrendererpixbuf.c

@@ -109,6 +109,7 @@ gtk_cell_renderer_pixbuf_init (GtkCellRendererPixbuf *cellpixbuf)
   priv = cellpixbuf->priv;
 
   priv->icon_helper = _gtk_icon_helper_new ();
+  _gtk_icon_helper_set_force_scale_pixbuf (priv->icon_helper, TRUE);
   priv->icon_size = GTK_ICON_SIZE_MENU;
 }