Recently chrome stopped to show Source Maps.
I had a some break with my project and now with the new version of gwt and chrome I don't see java sources in source tab.
I'm using super dev mode. Compiled file (*.cache.js) that I receive from Code Server contains header for Source Maps:
X-SourceMap:/sourcemaps/Simulation/gwtSourceMap.json
Code Server doesn't print that it has sent Source Maps (as it was before), only that Compilation was successful
I have: gwt version 2.5.0 Chrome verson 25.0.1364.172 Ubuntu 12.04 LTS (but the problem is reproduced in Windows and MacOS as well)
I guess you hit https://code.google.com/p/google-web-toolkit/issues/detail?id=7725
Try to update to 2.5.1.