[Sync] Replace typedef with using.

components/sync/engine/model_safe_worker.h

Index: components/sync/engine/model_safe_worker.h
diff --git a/components/sync/engine/model_safe_worker.h b/components/sync/engine/model_safe_worker.h
index 7165621318f77916f676a9181b4bf3acac8e992e..1565aa279d66eabc45ea9ba71b43c592e7bba767 100644
--- a/components/sync/engine/model_safe_worker.h
+++ b/components/sync/engine/model_safe_worker.h
@@ -22,7 +22,7 @@ class DictionaryValue;
 
 namespace syncer {
 
-typedef base::Callback<enum SyncerError(void)> WorkCallback;
+using WorkCallback = base::Callback<enum SyncerError(void)>;
 
 enum ModelSafeGroup {
   GROUP_PASSIVE = 0,   // Models that are just "passively" being synced; e.g.
@@ -91,7 +91,7 @@ class ModelSafeWorker : public base::RefCountedThreadSafe<ModelSafeWorker> {
 // A map that details which ModelSafeGroup each ModelType
 // belongs to.  Routing info can change in response to the user enabling /
 // disabling sync for certain types, as well as model association completions.
-typedef std::map<ModelType, ModelSafeGroup> ModelSafeRoutingInfo;
+using ModelSafeRoutingInfo = std::map<ModelType, ModelSafeGroup>;
 
 // Caller takes ownership of return value.
 std::unique_ptr<base::DictionaryValue> ModelSafeRoutingInfoToValue(