switch mediaGalleries to .idl api definition

chrome/renderer/resources/extensions/experimental.media_galleries_custom_bindings.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.
 
 // Custom bindings for the Media Gallery API.
 
 var mediaGalleriesNatives = requireNative('experimental_mediaGalleries');
 
 var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 
@@ skipping 13 matching lines @@
     }
     if (request.callback)
       request.callback(result);
     request.callback = null;
   });
 
   // extractEmbeddedThumbnails uses a renderer side handler so that it can
   // synchronously return a result.  The result object's state is computable
   // from the function's input.
   apiFunctions.setHandleRequest('extractEmbeddedThumbnails',
-                                 function(fileEntry) {
+                                function(fileEntry) {
     return mediaGalleriesNatives.ExtractEmbeddedThumbnails(fileEntry);
   });
 });