Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/docs/templates/intros/webRequest.html

-<p id="classSummary">
-Use the <code>chrome.webRequest</code> module to intercept, block,
-or modify requests in-flight and to observe and analyze traffic.
-</p>
-
 <h2 id="manifest">Manifest</h2>
 <p>You must declare the "webRequest" permission in the <a
   href="manifest.html">extension manifest</a> to use the web request
 API, along with <a href="declare_permissions.html">host permissions</a>
 for any hosts whose network requests you want to access. If you want to
 use the web request API in a blocking fashion, you need to request
 the "webRequestBlocking" permission in addition.
 For example:</p>
 <pre>{
   "name": "My extension",
@@ skipping 274 matching lines @@
       }
     }
     return {requestHeaders: details.requestHeaders};
   },
   {urls: ["&lt;all_urls&gt;"]},
   ["blocking", "requestHeaders"]);
 </pre>
 
 <p> For more example code, see the <a href="samples.html#webrequest">web request
 samples</a>.</p>