You're right: the chart packages look like they're missing.
For now, take a look at the standard JavaDoc docs for Ext GWT 2.2.5 at http://dev.sencha.com/deploy/gxt-2.2.5/docs/api/. I've checked, and these do definitely include the charts packages. We'll check to make sure the charts packages are in the docs app the next time we generate it. Thanks for posting and letting us know.