With a quick look your configuration looks just fine. Are you sure it is not working? Sometimes chromes network inspector is bit hard to follow. You could re-check the result in Incognito mode or with Firefox.
That sure is just jetty configuration issue, has nothing to do with Vaadin. Have you checked if the log gives any hints? You could also try enabling the servlet filter with servlet 3 style annotation, might be less prone for typos. Here is
one example of such, but uses ehcache version of gzip filter though.