title: Add class to body tag using diazo with notheme
body: <p>i'm displaying the content of a document in an overlay using
  <code>plone/document?ajax_load=True&amp;ajax_include_head=True</code> as the src for an iframe.</p>
  
  <p>in development mode appending <code>&amp;diazo.off=1</code> did the trick.
  on the production server this sadly does not work, so i added the
  ajax_load parameter as suggested in the <a href="http://pypi.python.org/pypi/plone.app.theming#theme-parameters" rel="nofollow noreferrer">documentation of plone.app.theming</a></p>
  
  <p>i wrapped all my directives in a  <code>&lt;rules if-not="$ajax_load"&gt;</code> element to make sure they are not applied (see code below)</p>
  
  <p>now i'd need to mark the body of the iframed page with a certain class to apply different styles (eg no background color for the body in overlays)</p>
  
  <p>the solution proposed for a <a href="https://stackoverflow.com/questions/6599993">nearly similar question</a>  does only work if you are using a theme with a body element having a class attribute to operate on.</p>
  
  <p>is there a way to add a class to the content without having a theme (using )?
  or do i have to supply an empty html document (index2.html) as theme and apply lots of rules to copy over css/js etc twice?</p>
  
  <pre><code>&lt;rules if="$ajax_load"&gt;
  
      &lt;!-- theme href="index.html" /--&gt;
  
      &lt;notheme /&gt;
  
  
      &lt;!-- only works when using a theme --&gt;
      &lt;before theme-children="/html/body"&gt;&lt;xsl:attribute name="class"&gt;&lt;xsl:value-of select="/html/body/@class"/&gt; my class&lt;/xsl:attribute&gt;&lt;/before&gt;
  
  
      &lt;!-- thought this could to the trick but does not work at all --&gt;
      &lt;xsl:template match="html/body"&gt;
      &lt;xsl:attribute name="class"&gt; foo&lt;/xsl:attribute&gt;
      &lt;/xsl:template&gt;
  
  
  &lt;/rules&gt;
  
  &lt;rules if-not="$ajax_load"&gt;
  
  
      &lt;theme href="index.html" /&gt;
  
      &lt;replace content="/html/head/title" theme="/html/head/title" /&gt;
      ...
  </code></pre>