[Sync] Replace typedef with using.

components/sync_sessions/lost_navigations_recorder.h

 // 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.
 
 #ifndef COMPONENTS_SYNC_SESSIONS_LOST_NAVIGATIONS_RECORDER_H_
 #define COMPONENTS_SYNC_SESSIONS_LOST_NAVIGATIONS_RECORDER_H_
 
 #include <map>
 #include <set>
 
 #include "base/macros.h"
 #include "components/sessions/core/session_id.h"
 #include "components/sync/model/local_change_observer.h"
 #include "components/sync/model/sync_change.h"
 #include "components/sync/protocol/session_specifics.pb.h"
 
 namespace sync_sessions {
 
 // Recorder class that tracks the number of navigations written locally that
 // aren't synced. This is done by recording set of locally observed navigations
 // and  reconciling these sets against what was ultimately synced. These
 // navigations ultimately feed chrome history, so losing them prevents them from
 // being reflected in the history page.
 class LostNavigationsRecorder : public syncer::LocalChangeObserver {
  public:
-  typedef SessionID::id_type id_type;
-  typedef std::set<id_type> IdSet;
+  using id_type = SessionID::id_type;
+  using IdSet = std::set<id_type>;
   enum RecorderState { RECORDER_STATE_NOT_SYNCING, RECORDER_STATE_SYNCING };
 
   LostNavigationsRecorder();
   ~LostNavigationsRecorder() override;
 
   // syncer::LocalChangeObserver implementation.
   void OnLocalChange(const syncer::syncable::Entry* current_entry,
                      const syncer::SyncChange& change) override;
 
  private:
@@ skipping 11 matching lines @@
   std::map<id_type, IdSet> recorded_navigation_ids_;
   // The set of navigation ids most recently recorded for each tab_id.
   std::map<id_type, IdSet> latest_navigation_ids_;
   // The maximum navigation_id recorded for each tab_id.
   std::map<id_type, id_type> max_recorded_for_tab_;
   DISALLOW_COPY_AND_ASSIGN(LostNavigationsRecorder);
 };
 };  // namespace sync_sessions
 
 #endif  // COMPONENTS_SYNC_SESSIONS_LOST_NAVIGATIONS_RECORDER_H_