[Sync] Replace typedef with using.

components/sync/engine_impl/commit_processor.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/commit_processor.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/metrics/histogram_macros.h"
 #include "components/sync/engine_impl/commit_contribution.h"
 #include "components/sync/engine_impl/commit_contributor.h"
 #include "components/sync/protocol/sync.pb.h"
 
 namespace syncer {
 
-typedef std::map<ModelType, size_t> TypeToIndexMap;
+using TypeToIndexMap = std::map<ModelType, size_t>;
 
 CommitProcessor::CommitProcessor(CommitContributorMap* commit_contributor_map)
     : commit_contributor_map_(commit_contributor_map) {}
 
 CommitProcessor::~CommitProcessor() {}
 
 void CommitProcessor::GatherCommitContributions(
     ModelTypeSet commit_types,
     size_t max_entries,
     bool cookie_jar_mismatch,
@@ skipping 26 matching lines @@
     }
     if (num_entries >= max_entries) {
       DCHECK_EQ(num_entries, max_entries)
           << "Number of commit entries exceeeds maximum";
       break;
     }
   }
 }
 
 }  // namespace syncer