Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/media_galleries.idl

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// 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).
+
+[availability=23]
 namespace mediaGalleries {
 
   [inline_doc] enum GetMediaFileSystemsInteractivity {
     // Do not act interactively.
     no,
     // Ask the user to manage permitted media galleries.
     yes,
     // Ask the user to manage permitted galleries only if the return set would
     // otherwise be empty.
     if_needed
@@ skipping 35 matching lines @@
     // configured or available, the callback will receive an empty array.
     static void getMediaFileSystems(optional MediaFileSystemsDetails details,
                                     MediaFileSystemsCallback callback);
 
     // Get metadata about a specific media file system.
     [nocompile] static MediaFileSystemMetadata getMediaFileSystemMetadata(
         [instanceOf=DOMFileSystem] object mediaFileSystem);
   };
 
 };