[Sync] Replace typedef with using.

components/sync/syncable/syncable_delete_journal.h

Index: components/sync/syncable/syncable_delete_journal.h
diff --git a/components/sync/syncable/syncable_delete_journal.h b/components/sync/syncable/syncable_delete_journal.h
index f1b45fa86f6f4b82c1b938c434c4e94ec004c3ee..da2b4c15eb0d808eac9f69e9ace9ce9288aeaa5c 100644
--- a/components/sync/syncable/syncable_delete_journal.h
+++ b/components/sync/syncable/syncable_delete_journal.h
@@ -31,8 +31,8 @@ class LessByID {
 // DeleteJournal::TakeSnapshotAndClear needs to remove the unique_ptr from the
 // set, and std::set::extract is only available in C++17. TODO(avi): Switch to
 // using a std::set when Chromium allows C++17 use.
-typedef std::map<const EntryKernel*, std::unique_ptr<EntryKernel>, LessByID>
-    JournalIndex;
+using JournalIndex =
+    std::map<const EntryKernel*, std::unique_ptr<EntryKernel>, LessByID>;
 
 // DeleteJournal manages deleted entries that are not in sync directory until
 // it's safe to drop them after the deletion is confirmed with native models.