Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/chrome_tests.gypi

 # 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.
 {
   'variables' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
       'common/pref_names.cc',
@@ skipping 952 matching lines @@
         'browser/extensions/api/idle/idle_apitest.cc',
         'browser/extensions/api/idltest/idltest_apitest.cc',
         'browser/extensions/api/input/input_apitest.cc',
         'browser/extensions/api/input_ime/input_ime_apitest_chromeos.cc',
         'browser/extensions/api/managed_mode/managed_mode_apitest.cc',
         'browser/extensions/api/management/management_api_browsertest.cc',
         'browser/extensions/api/management/management_apitest.cc',
         'browser/extensions/api/management/management_browsertest.cc',
         'browser/extensions/api/media_galleries/media_galleries_apitest.cc',
         'browser/extensions/api/media_galleries_private/media_galleries_private_apitest.cc',
+        'browser/extensions/api/media_galleries_private/media_galleries_watch_apitest.cc',
         'browser/extensions/api/messaging/native_messaging_apitest_posix.cc',
         'browser/extensions/api/metrics/metrics_apitest.cc',
         'browser/extensions/api/module/module_apitest.cc',
         'browser/extensions/api/notification/notification_apitest.cc',
         'browser/extensions/api/omnibox/omnibox_apitest.cc',
         'browser/extensions/api/page_capture/page_capture_apitest.cc',
         'browser/extensions/api/permissions/permissions_apitest.cc',
         'browser/extensions/api/preference/preference_apitest.cc',
         'browser/extensions/api/processes/processes_apitest.cc',
         'browser/extensions/api/proxy/proxy_apitest.cc',
@@ skipping 1844 matching lines @@
             'sync_integration_tests.isolate',
           ],
           'sources': [
             'sync_integration_tests.isolate',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }