[Sync] Replace typedef with using.

components/sync/syncable/change_reorder_buffer.h

Index: components/sync/syncable/change_reorder_buffer.h
diff --git a/components/sync/syncable/change_reorder_buffer.h b/components/sync/syncable/change_reorder_buffer.h
index e1873c60d072a55acb542d071a39eed920aa4fb2..e79a7171b9c59722bb74da77d966cd2418a5393c 100644
--- a/components/sync/syncable/change_reorder_buffer.h
+++ b/components/sync/syncable/change_reorder_buffer.h
@@ -67,10 +67,10 @@ class ChangeReorderBuffer {
 
  private:
   class Traversal;
-  typedef std::map<int64_t, ChangeRecord::Action> OperationMap;
-  typedef std::map<int64_t, sync_pb::EntitySpecifics> SpecificsMap;
-  typedef std::map<int64_t, linked_ptr<ExtraPasswordChangeRecordData>>
-      ExtraDataMap;
+  using OperationMap = std::map<int64_t, ChangeRecord::Action>;
+  using SpecificsMap = std::map<int64_t, sync_pb::EntitySpecifics>;
+  using ExtraDataMap =
+      std::map<int64_t, linked_ptr<ExtraPasswordChangeRecordData>>;
 
   // Stores the items that have been pushed into the buffer, and the type of
   // operation that was associated with them.