Add missing task_queue.cc to sync_core GN sources list.

sync/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//testing/test.gni")
 
 component("sync") {
   public_deps = [
     ":sync_core",
@@ skipping 115 matching lines @@
     "internal_api/attachments/attachment_service_proxy.cc",
     "internal_api/attachments/attachment_service_proxy_for_test.cc",
     "internal_api/attachments/attachment_store_frontend.cc",
     "internal_api/attachments/attachment_uploader.cc",
     "internal_api/attachments/attachment_uploader_impl.cc",
     "internal_api/attachments/attachment_util.cc",
     "internal_api/attachments/fake_attachment_downloader.cc",
     "internal_api/attachments/fake_attachment_uploader.cc",
     "internal_api/attachments/in_memory_attachment_store.cc",
     "internal_api/attachments/on_disk_attachment_store.cc",
+    "internal_api/attachments/task_queue.cc",
     "internal_api/base_node.cc",
     "internal_api/base_transaction.cc",
     "internal_api/change_record.cc",
     "internal_api/change_reorder_buffer.cc",
     "internal_api/change_reorder_buffer.h",
     "internal_api/debug_info_event_listener.cc",
     "internal_api/debug_info_event_listener.h",
     "internal_api/delete_journal.cc",
     "internal_api/events/commit_request_event.cc",
     "internal_api/events/commit_response_event.cc",
@@ skipping 664 matching lines @@
     deps = [
       ":fake_server_jni",
       ":sync_core",
       ":test_support_sync_fake_server",
       "//base",
       "//sync/protocol:protocol",
       "//testing/gtest",
     ]
   }
 }