class Haml::HTML

def on_html_condcomment(condition, content, revealed = false)

This dispatcher supports Haml's "revealed" conditional comment. 
def on_html_condcomment(condition, content, revealed = false)
  on_html_comment [:multi,
                   [:static, "[#{condition}]>#{'<!-->' if revealed}"],
                   content,
                   [:static, "#{'<!--' if revealed}<![endif]"]]
end