Revert of [Sync] IWYU cleanup.

components/sync/engine_impl/loopback_server/loopback_server_entity.cc

 // 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.
 
 #include "components/sync/engine_impl/loopback_server/loopback_server_entity.h"
 
+#include <stdint.h>
+
 #include <limits>
 #include <memory>
+#include <string>
 #include <vector>
 
 #include "base/guid.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "components/sync/base/model_type.h"
 #include "components/sync/engine_impl/loopback_server/persistent_bookmark_entity.h"
 #include "components/sync/engine_impl/loopback_server/persistent_permanent_entity.h"
 #include "components/sync/engine_impl/loopback_server/persistent_tombstone_entity.h"
 #include "components/sync/engine_impl/loopback_server/persistent_unique_client_entity.h"
+#include "components/sync/protocol/sync.pb.h"
 #include "net/base/net_errors.h"
 #include "net/http/http_status_code.h"
 
 using std::string;
 using std::vector;
 
 using syncer::ModelType;
 
 namespace {
 // The separator used when formatting IDs.
@@ skipping 137 matching lines @@
 }
 
 void LoopbackServerEntity::SerializeAsLoopbackServerEntity(
     sync_pb::LoopbackServerEntity* entity) const {
   entity->set_type(GetLoopbackServerEntityType());
   entity->set_model_type(static_cast<int64_t>(GetModelType()));
   SerializeAsProto(entity->mutable_entity());
 }
 
 }  // namespace syncer