sync: remove use of protobuf extensions in protocol to reduce static init overhead.

chrome/browser/sync/api/sync_data.cc

Index: chrome/browser/sync/api/sync_data.cc
diff --git a/chrome/browser/sync/api/sync_data.cc b/chrome/browser/sync/api/sync_data.cc
index 08117ac2f67f24611a3372f1e93df3d1e9b64d9c..7905e77296c1b2a088c1503d2893519783071d86 100644
--- a/chrome/browser/sync/api/sync_data.cc
+++ b/chrome/browser/sync/api/sync_data.cc
@@ -56,7 +56,7 @@ SyncData SyncData::CreateLocalDelete(
     const std::string& sync_tag,
     syncable::ModelType datatype) {
   sync_pb::EntitySpecifics specifics;
-  syncable::AddDefaultExtensionValue(datatype, &specifics);
+  syncable::AddDefaultFieldValue(datatype, &specifics);
   return CreateLocalData(sync_tag, "", specifics);
 }