No information for the plugin 'gerrit' is available. It may have been removed from distribution.
This plugin integrates Gerrit Code Review to Hudson. It just marks whether the build was successful or not. You have to use Git plugin (or something else) for checking out change-sets from Gerrit, even though it's terribly slow because there's a lot of branches in Gerrit (Git plugin tries to determine "...list of 'tip' branches (I.E. branches that aren't included entirely within another branch)". This is pretty slow.
After build, the plugin just checks what revision is in workspace at the moment and uses Gerrits ssh command line tools for marking the result.
*Implement polling and fetching (or preferably make current git plugin faster)