[Sync] Replace typedef with using.

components/sync/engine/net/network_time_update_callback.h

Index: components/sync/engine/net/network_time_update_callback.h
diff --git a/components/sync/engine/net/network_time_update_callback.h b/components/sync/engine/net/network_time_update_callback.h
index ff3c5b8ddda641df948f6e05267e37ab6395d0c0..580524b2a4b9bf1f26433261c10dab5c9d6f8cd1 100644
--- a/components/sync/engine/net/network_time_update_callback.h
+++ b/components/sync/engine/net/network_time_update_callback.h
@@ -19,9 +19,8 @@ namespace syncer {
 // const base::Time& network_time - the new network time.
 // const base::TimeDelta& resolution - how precise the reading is.
 // const base::TimeDelta& latency - the http request's latency.
-typedef base::Callback<
-    void(const base::Time&, const base::TimeDelta&, const base::TimeDelta&)>
-    NetworkTimeUpdateCallback;
+using NetworkTimeUpdateCallback = base::Callback<
+    void(const base::Time&, const base::TimeDelta&, const base::TimeDelta&)>;
 
 }  // namespace syncer