Jetty 7 - Does it perform gzip compression by default

Jetty 7 - Does it perform gzip compression by default

I have a web application built on google's GWT framework. I was planning
on setting up the Jetty GzipFilter in order to make the response
compressed. Here, i noticed, after checking on firebug and TCP mon that
even without the filter, the responses are gzipped.
I checked the xml configuration files in jetty and could not find any
default gzip filter defined anywhere. Can you please tell me if Jetty-7
does gzip compression by default?
I'm using jetty version 7.4.5. If additional information is required,
please let me know and I shall provide.