user/src/com/google/gwt/logging/LogImpl.gwt.xml

<module>
  <source path="impl" />
  
  <!-- Set up and handle the gwt.logging property -->
  <define-property name="gwt.logging.enabled" values="TRUE, FALSE" />
  <replace-with class="com.google.gwt.logging.impl.LoggerImplRegular">
    <when-type-is class="com.google.gwt.logging.impl.LoggerImplNull"/>
    <when-property-is name="gwt.logging.enabled" value="TRUE" />
  </replace-with>
  <replace-with class="com.google.gwt.logging.impl.LevelImplRegular">
    <when-type-is class="com.google.gwt.logging.impl.LevelImplNull"/>
    <when-property-is name="gwt.logging.enabled" value="TRUE" />
  </replace-with>
  
  <set-property name="gwt.logging.enabled" value="FALSE"/> 
  
</module>