Delete deprecated synced notifications code

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 2013 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': {
     'chrome_browser_extensions_chromeos_sources': [
       'browser/extensions/api/diagnostics/diagnostics_api.cc',
       'browser/extensions/api/diagnostics/diagnostics_api.h',
       'browser/extensions/api/diagnostics/diagnostics_api_chromeos.cc',
@@ skipping 432 matching lines @@
       'browser/extensions/api/storage/syncable_settings_storage.cc',
       'browser/extensions/api/storage/syncable_settings_storage.h',
       'browser/extensions/api/streams_private/streams_private_api.cc',
       'browser/extensions/api/streams_private/streams_private_api.h',
       'browser/extensions/api/sync_file_system/extension_sync_event_observer.cc',
       'browser/extensions/api/sync_file_system/extension_sync_event_observer.h',
       'browser/extensions/api/sync_file_system/sync_file_system_api.cc',
       'browser/extensions/api/sync_file_system/sync_file_system_api.h',
       'browser/extensions/api/sync_file_system/sync_file_system_api_helpers.cc',
       'browser/extensions/api/sync_file_system/sync_file_system_api_helpers.h',
-      'browser/extensions/api/synced_notifications_private/synced_notifications_private_api.cc',
-      'browser/extensions/api/synced_notifications_private/synced_notifications_private_api.h',
-      'browser/extensions/api/synced_notifications_private/synced_notifications_shim.cc',
-      'browser/extensions/api/synced_notifications_private/synced_notifications_shim.h',
       'browser/extensions/api/system_indicator/system_indicator_api.h',
       'browser/extensions/api/system_indicator/system_indicator_manager.cc',
       'browser/extensions/api/system_indicator/system_indicator_manager.h',
       'browser/extensions/api/system_indicator/system_indicator_manager_factory.cc',
       'browser/extensions/api/system_indicator/system_indicator_manager_factory.h',
       'browser/extensions/api/system_private/system_private_api.cc',
       'browser/extensions/api/system_private/system_private_api.h',
       'browser/extensions/api/tab_capture/tab_capture_api.cc',
       'browser/extensions/api/tab_capture/tab_capture_api.h',
       'browser/extensions/api/tab_capture/tab_capture_registry.cc',
@@ skipping 662 matching lines @@
           ],
         }, {  # use_brlapi==0
           'sources': [
             'browser/extensions/api/braille_display_private/braille_controller_stub.cc',
           ],
         }],
       ],
     },
   ],
 }