elemental/src/elemental/Json.gwt.xml

<?xml version="1.0" encoding="UTF-8" ?>
<module>
  <inherits name="com.google.gwt.core.Core" />
  <inherits name="elemental.Collections" />

  <source path="js/json" />
  <source path='json'/>
  <super-source path="super" includes="elemental/json/**/*"/>
</module>