Fixes r 2418 by removing infinite loop on eventToString->evt.getString()->eventToString().  Instead call impl.eventToString.
review by:jlabanca(desk check on Friday, was waiting on clean build to commit...)

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2864 8db76d5a-ed1c-0410-87a9-c151d255dfc7