Sorry - if you get this twice - I accidentally have hit the PostMessage button before and had to delete the message again.
Just tried to dig deeper here: the gwt-user.jar
contains a file /org/hibernate/validator/HibernateValidator.gwt.xml.
In the GWT-file I see a section
...
<source path="engine">
<include name="ConstraintViolationImpl*.java"/>
<include name="ValidationSupport.java"/>
<include name="NodeImpl.java"/>
<include name="PathImpl*.java"/>
</source>
...