src/main/java/com/google/gwt/site/webapp/GWTProjectSuperDevMode.gwt.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC "-//Google Inc.//DTD Google Web Toolkit//EN" "http://google-web-toolkit.googlecode.com/svn/trunk/distro-source/core/src/gwt-module.dtd">
<module rename-to="gwtproject">
    <inherits name="com.google.gwt.site.webapp.GWTProject" />

    <!-- super dev mode -->
    <set-property name="user.agent" value="safari"/>

    <add-linker name="xsiframe"/>
    <set-configuration-property name="devModeRedirectEnabled" value="true"/>
    <set-property name="compiler.useSourceMaps" value="true"/>
</module>