Pref service: create service at browser startup

components/sync_preferences/BUILD.gn

 # 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.
 
 import("//build/config/features.gni")
 
 static_library("sync_preferences") {
   sources = [
     "pref_model_associator.cc",
     "pref_model_associator.h",
     "pref_model_associator_client.h",
     "pref_service_syncable.cc",
     "pref_service_syncable.h",
     "pref_service_syncable_factory.cc",
     "pref_service_syncable_factory.h",
     "pref_service_syncable_observer.h",
     "synced_pref_change_registrar.cc",
     "synced_pref_change_registrar.h",
     "synced_pref_observer.h",
   ]
 
   deps = [
     "//base",
     "//components/pref_registry",
     "//components/prefs",
     "//components/sync",
+    "//services/preferences/public/cpp",
   ]
 
   if (!is_ios) {
     deps += [ "//components/policy/core/browser" ]
   }
 }
 
 static_library("test_support") {
   testonly = true
   sources = [
@@ skipping 22 matching lines @@
   deps = [
     ":sync_preferences",
     ":test_support",
     "//components/pref_registry",
     "//components/prefs",
     "//components/sync",
     "//components/sync:test_support_model",
     "//testing/gtest",
   ]
 }