LGTM w/some nits it looks like CfgBuild could be made such that individual visit methods are a bit more self-contained. It shouldn't be possible for a visitor to an inner loop to modify the unlabeled break/continue statements of an outer loop, etc. Removing them and replacing them at the end, seems a bit of a hack.
Might be good to have some tests which test nested loops of different types, e.g. a for loop inside a while loop, etc. http://gwt-code-reviews.appspot.com/1447824/ -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
