[Sync] Create UserEventService.

chrome/browser/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/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
@@ skipping 1301 matching lines @@
     "sync/sessions/sync_sessions_router_tab_helper.cc",
     "sync/sessions/sync_sessions_router_tab_helper.h",
     "sync/sessions/sync_sessions_web_contents_router.cc",
     "sync/sessions/sync_sessions_web_contents_router.h",
     "sync/sessions/sync_sessions_web_contents_router_factory.cc",
     "sync/sessions/sync_sessions_web_contents_router_factory.h",
     "sync/supervised_user_signin_manager_wrapper.cc",
     "sync/supervised_user_signin_manager_wrapper.h",
     "sync/sync_startup_tracker.cc",
     "sync/sync_startup_tracker.h",
+    "sync/user_event_service_factory.cc",
+    "sync/user_event_service_factory.h",
     "tab_contents/navigation_metrics_recorder.cc",
     "tab_contents/navigation_metrics_recorder.h",
     "tab_contents/tab_util.cc",
     "tab_contents/tab_util.h",
     "task_manager/web_contents_tags.cc",
     "task_manager/web_contents_tags.h",
     "task_profiler/task_profiler_data_serializer.cc",
     "task_profiler/task_profiler_data_serializer.h",
     "themes/theme_service_win.cc",
     "themes/theme_service_win.h",
@@ skipping 3368 matching lines @@
       "media/pepper_cdm_test_constants.cc",
       "media/pepper_cdm_test_constants.h",
     ]
   }
 }
 
 service_manifest("preferences_forwarder_manifest") {
   name = "preferences_forwarder"
   source = "prefs/forwarder_manifest.json"
 }