switch mediaGalleries to .idl api definition

chrome/common/extensions/docs/js/api_page_generator.js

 // 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.
 
 /**
  * @fileoverview This file is the controller for generating extension
  * doc pages.
  *
  * It expects to have available via XHR (relative path):
  *   1) API_TEMPLATE which is the main template for the api pages.
@@ skipping 28 matching lines @@
   '../../api/experimental_accessibility.json',
   '../../api/experimental_app.json',
   '../../api/experimental_bluetooth.json',  // autogenerated
   '../../api/experimental_bookmark_manager.json',
   '../../api/experimental_discovery.json',  // autogenerated
   '../../api/experimental_font_settings.json',
   '../../api/experimental_identity.json',  // autogenerated
   '../../api/experimental_infobars.json',
   '../../api/experimental_input_virtual_keyboard.json',
   '../../api/experimental_keybinding.json',
-  '../../api/experimental_media_galleries.json',
+  '../../api/experimental_media_galleries.json',  // autogenerated
   '../../api/experimental_offscreen_tabs.json',
   '../../api/experimental_processes.json',
   '../../api/experimental_rlz.json',
   '../../api/experimental_serial.json',  // autogenerated
   '../../api/experimental_speech_input.json',
   '../../api/experimental_socket.json',  // autogenerated
   '../../api/experimental_usb.json',  // autogenerated
   '../../api/extension.json',
   '../../api/file_browser_handler.json',
   '../../api/file_browser_private.json',
@@ skipping 794 matching lines @@
   }
   if (a.name > b.name) {
     return 1;
   }
   return 0;
 }
 
 function disableDocs(obj) {
   return !!obj.nodoc;
 }