[Sync] Refactor sync manager into interface.

sync/internal_api/sync_manager_factory.cc

+// Copyright (c) 2012 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.
+
+#include "sync/internal_api/public/sync_manager_factory.h"
+
+#include "sync/internal_api/sync_manager_impl.h"
+
+namespace syncer {
+
+SyncManagerFactory::SyncManagerFactory() {
+}
+
+SyncManagerFactory::~SyncManagerFactory() {
+}
+
+scoped_ptr<SyncManager> SyncManagerFactory::CreateSyncManager(
+      const std::string name) {
+  return scoped_ptr<SyncManager>(new SyncManagerImpl(name));
+}
+
+}  // namespace syncer