Port ChromeSyncShell build rules to GN

sync/protocol/protocol.gypi

 # Copyright 2015 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': {
     # The directory that contains the sync protocol buffer definitions.
     # This variable can be overridden for other builds that require the proto
     # files to be stored in an intermediate directory.
     'sync_proto_sources_dir%': '.',
 
     # The list of sync protocol buffer definitions.
     'sync_proto_source_paths': [
-      # NOTE: If you add a file to this list, also add it to
-      # sync/protocol/BUILD.gn
       # TODO(pvalenzuela): Eliminate the requirement to update the GN file.
       '<(sync_proto_sources_dir)/app_notification_specifics.proto',
       '<(sync_proto_sources_dir)/app_setting_specifics.proto',
       '<(sync_proto_sources_dir)/app_specifics.proto',
       '<(sync_proto_sources_dir)/app_list_specifics.proto',
       '<(sync_proto_sources_dir)/article_specifics.proto',
       '<(sync_proto_sources_dir)/attachments.proto',
       '<(sync_proto_sources_dir)/autofill_specifics.proto',
       '<(sync_proto_sources_dir)/bookmark_specifics.proto',
       '<(sync_proto_sources_dir)/client_commands.proto',
@@ skipping 25 matching lines @@
       '<(sync_proto_sources_dir)/synced_notification_app_info_specifics.proto',
       '<(sync_proto_sources_dir)/synced_notification_specifics.proto',
       '<(sync_proto_sources_dir)/test.proto',
       '<(sync_proto_sources_dir)/theme_specifics.proto',
       '<(sync_proto_sources_dir)/typed_url_specifics.proto',
       '<(sync_proto_sources_dir)/unique_position.proto',
       '<(sync_proto_sources_dir)/wifi_credential_specifics.proto',
     ],
   },
 }