class UserAgent::Browsers::InternetExplorer

def chromeframe

or as a separate product with a version
as of 4.0 it can declare itself versioned in a comment
Before version 4.0, Chrome Frame declared itself (unversioned) in a comment; 
def chromeframe
  cf = application.comment.include?("chromeframe") || detect_product("chromeframe")
  return cf if cf
  cf_comment = application.comment.detect { |c| c['chromeframe/'] }
  cf_comment ? UserAgent.new(*cf_comment.split('/', 2)) : nil
end