Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/chrome_browser_extensions.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.
 
 {
   'targets': [
     {
       'target_name': 'browser_extensions',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 218 matching lines @@
         'browser/extensions/api/managed_mode/managed_mode_api_factory.cc',
         'browser/extensions/api/managed_mode/managed_mode_api_factory.h',
         'browser/extensions/api/management/management_api.cc',
         'browser/extensions/api/management/management_api.h',
         'browser/extensions/api/management/management_api_constants.cc',
         'browser/extensions/api/management/management_api_constants.h',
         'browser/extensions/api/management/management_api_factory.cc',
         'browser/extensions/api/management/management_api_factory.h',
         'browser/extensions/api/media_galleries/media_galleries_api.cc',
         'browser/extensions/api/media_galleries/media_galleries_api.h',
+        'browser/extensions/api/media_galleries_private/gallery_watch_manager.cc',
+        'browser/extensions/api/media_galleries_private/gallery_watch_manager.h',
+        'browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.cc',
+        'browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h',        
         'browser/extensions/api/media_galleries_private/media_galleries_private_api.cc',
         'browser/extensions/api/media_galleries_private/media_galleries_private_api.h',
         'browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.cc',
         'browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.h',
         'browser/extensions/api/media_galleries_private/media_galleries_private_event_router.cc',
         'browser/extensions/api/media_galleries_private/media_galleries_private_event_router.h',
         'browser/extensions/api/messaging/extension_message_port.cc',
         'browser/extensions/api/messaging/extension_message_port.h',
         'browser/extensions/api/messaging/message_service.cc',
         'browser/extensions/api/messaging/message_service.h',
@@ skipping 708 matching lines @@
           'msvs_settings': {
             'VCLinkerTool': {
               'SubSystem': '2',  # Set /SUBSYSTEM:WINDOWS
             },
           },
         },
       ],
     }, ],  # 'OS=="win"'
   ],  # 'conditions'
 }