Move MediaGalleries.getMediaFileSystems back to experimental for M22

chrome/test/data/extensions/api_test/media_galleries/no_access/test.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.
 
-var mediaGalleries = chrome.mediaGalleries;
+var mediaGalleries = chrome.experimental.mediaGalleries;
 
 var mediaFileSystemsDirectoryEntryCallback = function(entries) {
   chrome.test.fail("Shouldn't have been able to get a directory listing.");
 };
 
 var mediaFileSystemsListCallback = function(results) {
   // There should be a "Pictures" directory on all desktop platforms.
   var expectedFileSystems = 1;
   // But not on Android and ChromeOS.
   if (/Android/.test(navigator.userAgent) || /CrOS/.test(navigator.userAgent))
     expectedFileSystems = 0;
   chrome.test.assertEq(expectedFileSystems, results.length);
   if (expectedFileSystems) {
     var dir_reader = results[0].root.createReader();
     dir_reader.readEntries(mediaFileSystemsDirectoryEntryCallback,
                            chrome.test.callbackPass());
   }
 };
 
 chrome.test.runTests([
   function getGalleries() {
     mediaGalleries.getMediaFileSystems(
         chrome.test.callbackPass(mediaFileSystemsListCallback));
   },
 ]);