[Sync] Replace typedef with using.

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 <algorithm>
 #include <limits>
 #include <set>
 #include <utility>
@@ skipping 83 matching lines @@
     ModelTypeToVersionMap::const_iterator it =
         request_from_version_.find(entity.GetModelType());
 
     return it == request_from_version_.end() ? false : it->second < version;
   }
 
   // Returns the minimum version seen across all types.
   int64_t GetMinVersion() const { return min_version_; }
 
  private:
-  typedef std::map<ModelType, int64_t> ModelTypeToVersionMap;
+  using ModelTypeToVersionMap = std::map<ModelType, int64_t>;
 
   // Creates an UpdateSieve.
   UpdateSieve(const ModelTypeToVersionMap request_from_version,
               const int64_t min_version)
       : request_from_version_(request_from_version),
         min_version_(min_version) {}
 
   // Maps data type IDs to the latest version seen for that type.
   const ModelTypeToVersionMap request_from_version_;
 
@@ skipping 432 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