Dynamically generate a heading for Extension Docs API pages

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

 <table class="intro">
   <tr>
     <th scope="col"></th>
     <th scope="col"></th>
   </tr>
   <tr>
-    <td><strong>Description:</strong></td>
-    <td>Use the <code>chrome.mediaGalleries</code> API
-    to access media files (images, video, audio)
-    from the user's local disks (with the user's consent).</td>
-  </tr>
-  <tr>
-    <td><strong>Availability:</strong></td>
-    <td>Google Chrome 23 (read permission)</td>
-  </tr>
-  <tr>
     <td><strong>Permissions:</strong></td>
     <td><code>"mediaGalleries": ["read"]</code>,
     <code>"mediaGalleries": ["read", "allAutoDetected"]</code><br>
     See <a href="#manifest">Manifest</a> below
     for more information.</td>
   </tr>
   <tr>
     <td><strong>Learn more:</strong></td>
     <td><a href="https://developers.google.com/live/shows/10479832/">Chrome Office Hours: The Media Galleries API</a></td>
   </tr>
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 <p>This permission will trigger an install time permission prompt
 and let the app read from all auto-detected media galleries on the
 user's computer. The user may add or remove galleries using the
 media gallery management dialog, after which the app will be able
 to read all the media files from galleries that the user has selected.</p>
 
 <p>Currently "read" is the only access type supported by
 this API. Read-write and add-file access with be implemented soon.</p>