The real reason for the problem that the just reverted change
was supposed to address is that testfilechooser uses show_all
to tease out places where composite dialogs don't properly
protect their internals against unintended showing. Well,
lets do that, then.
<child>
<object class="GtkBox" id="action_box">
<property name="visible">True</property>
+ <property name="no-show-all">True</property>
<property name="can_focus">False</property>
<style>
<class name="dialog-action-box"/>