This only works for scalable icons, but breaks if we fall
back to pngs.
<object class="GtkImage">
<property name="visible">True</property>
<property name="icon-name">list-add-symbolic</property>
- <property name="icon-size">0</property>
<property name="use-fallback">True</property>
</object>
</child>
<object class="GtkImage">
<property name="visible">True</property>
<property name="icon-name">list-remove-symbolic</property>
- <property name="icon-size">0</property>
<property name="use-fallback">True</property>
</object>
</child>