Add server-timing to timing info struct

fetch.bs

@@ -263,6 +263,9 @@ following <a for=struct>items</a>: [[RESOURCE-TIMING]] [[NAVIGATION-TIMING]]
 
  <dt><dfn export for="fetch timing info">final connection timing info</dfn> (default null)
  <dd>Null or a <a for=/>connection timing info</a>.
+
+ <dt><dfn export for="fetch timing info">server timing headers</dfn> (default an empty list)
+ <dd>A <a for=/>list</a> of strings.
 </dl>
 
 <p>To
@@ -4296,6 +4299,10 @@ steps:
    <a for="fetch params">timing info</a>.</p></li>
   </ol>
  </li>
+ <li><p>Otherwise, set <var>response</var>'s <a for=response>timing info</a>'s
+ <a for="fetch timing info">server timing headers</a> to the result of
+ <a for="header list">getting, decoding, and splitting</a> `<code>Server-Timing</code>` from
+ <var>response</var>'s <a for=response>header list</a>.</p></li>
 
  <li>
   <p>Let <var>processResponseEndOfBody</var> be the following steps: