Add class to WordPress admin bar?

How can I to add a wrapper class to the WordPress admin bar?

I would like to center the contents to the same width as my theme.

There isn’t a filter/wrapper for the admin bar CSS that you can plug into , the function is simply

  function wp_admin_bar_header() { ?>
  <style type="text/css" media="print">#wpadminbar { display:none; }</style>

You can over ride the CSS using !important or use jQuery to prepend a class/id to the bar.

Something like:

jQuery("<div id='custom-width'></div>").prependTo("#wpadminbar");