gwt-dev.jar and gwt-user.jar were extracted from http://google-web-toolkit.googlecode.com/files/gwt-2.4.0.zip

Steps:
1. Unzip the GWT zip file
2. Copy gwt-dev.jar and gwt-user.jar into this directory
3. Delete gwt-dev-modified.jar and gwt-user-modified.jar from this directory
4. run ./createApiCheckerReferenceJars.sh
   - Ignore the benign error about finding com/google/web.  The directory only exists in gwt-user.
5. Delete gwt-dev.jar and gwt-user.jar from this directory
6. Commit the new gwt-dev-modified.jar and gwt-user-modified.jar