update docs with prerender timers

doc/api/RT.html

@@ -218,11 +218,15 @@ <h2 id="beacon">Beacon Parameters</h2>
 This plugin adds the following parameters to the beacon:
 </p>
 <dl>
-<dt>t_done</dt> <dd><strong>[optional]</strong> Round trip time of the page.</dd>
+<dt>t_done</dt> <dd><strong>[optional]</strong> Perceived load time of the page.</dd>
 <dt>t_page</dt> <dd><strong>[optional]</strong> Time taken from the head of the page to page_ready.  Requires dev effort.</dd>
 <dt>t_other</dt> <dd><strong>[optional]</strong> Comma separated list of additional timers set by page developer.  Each timer is of the format <code>name|value</code></dd>
+<dt>t_load</dt> <dd><strong>[optional]</strong> If the page were prerendered, this is the time to fetch and prerender the page.</dd>
+<dt>t_prerender</dt> <dd><strong>[optional]</strong> If the page were prerendered, this is the time from start of prefetch to the actual page display.  It may only be useful for debugging.</dd>
+<dt>t_postrender</dt> <dd><strong>[optional]</strong> If the page were prerendered, this is the time from prerender finish to actual page display.  It may only be useful for debugging.</dd>
 <dt>r</dt> <dd>URL of page that set the start time of the beacon.</dd>
 <dt>r2</dt> <dd><strong>[optional]</strong> URL of referrer of current page.  Only set if different from <code>r</code> and <code>strict_referrer</code> has been explicitly turned off.</dd>
+<dt>rt.start</dt> <dd>Specifies where the start time came from.  May be one of <code>cookie</code> for the start cookie, <code>navigation</code> for the W3C navigation timing API, <code>csi</code> for older versions of Chrome or <code>gtb</code> for the Google Toolbar.</dd>
 </dl>