Revert of [Sync] IWYU cleanup.

components/sync/engine_impl/loopback_server/loopback_server.cc

 // Copyright 2016 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.h"
 
+#include <stdint.h>
+
 #include <algorithm>
 #include <limits>
+#include <memory>
 #include <set>
+#include <string>
 #include <utility>
+#include <vector>
 
 #include "base/files/file_util.h"
 #include "base/guid.h"
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.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 "net/base/net_errors.h"
 #include "net/http/http_status_code.h"
 
 using std::string;
 using std::vector;
 
@@ skipping 510 matching lines @@
       // write.
       LOG(ERROR) << "Loopback sync can not read the persistent state file.";
       return false;
     }
   }
   LOG(WARNING) << "Loopback sync persistent state file does not exist.";
   return false;
 }
 
 }  // namespace syncer