[Sync] SyncEngine refactor part 2: SyncServiceBase.

components/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/buildflag_header.gni")
 import("//build/config/features.gni")
 import("//components/sync/protocol/protocol_sources.gni")
 import("//testing/test.gni")
 
 static_library("sync") {
@@ skipping 132 matching lines @@
     "driver/startup_controller.h",
     "driver/sync_api_component_factory.h",
     "driver/sync_client.cc",
     "driver/sync_client.h",
     "driver/sync_driver_switches.cc",
     "driver/sync_driver_switches.h",
     "driver/sync_error_controller.cc",
     "driver/sync_error_controller.h",
     "driver/sync_service.cc",
     "driver/sync_service.h",
+    "driver/sync_service_base.cc",
+    "driver/sync_service_base.h",
     "driver/sync_service_observer.cc",
     "driver/sync_service_observer.h",
     "driver/sync_service_utils.cc",
     "driver/sync_service_utils.h",
     "driver/sync_stopped_reporter.cc",
     "driver/sync_stopped_reporter.h",
     "driver/sync_type_preference_provider.h",
     "driver/sync_util.cc",
     "driver/sync_util.h",
     "driver/user_selectable_sync_type.h",
@@ skipping 973 matching lines @@
     deps = [
       ":fake_server_jni",
       ":sync",
       ":test_support_fake_server",
       "//base",
       "//testing/gtest",
       "//url:url",
     ]
   }
 }