GtkDialog: Be a little more careful about button placement
We were applying response based heuristics, even if the button is explicitly put in the headerbar. That broke button placement in some epiphany dialogs, such as the Cookies one. Therefore, restrict the heuristics to action widgets that are added through gtk_widget_add_action_widget() or <child type="action">, where it is not possible to specify placement explicitly.
Showing with 16 additions and 4 deletions