Move PrefStoreManagerImpl into //services/preferences.

services/preferences/public/cpp/pref_service_main.h

+// Copyright 2017 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.
+
+#ifndef SERVICES_PREFERENCES_PUBLIC_CPP_PREF_SERVICE_MAIN_H_
+#define SERVICES_PREFERENCES_PUBLIC_CPP_PREF_SERVICE_MAIN_H_
+
+#include <memory>
+#include <set>
+
+#include "base/memory/ref_counted.h"
+#include "components/prefs/pref_value_store.h"
+
+namespace base {
+class SequencedWorkerPool;
+}
+
+namespace service_manager {
+class Service;
+}
+
+namespace prefs {
+
+std::unique_ptr<service_manager::Service> CreatePrefService(
+    std::set<PrefValueStore::PrefStoreType> expected_pref_stores,
+    scoped_refptr<base::SequencedWorkerPool> worker_pool);
+
+}  // namespace prefs
+
+#endif  // SERVICES_PREFERENCES_PUBLIC_CPP_PREF_SERVICE_MAIN_H_