Populate versions on individual nodes in sync model and native bookmark model.

sync/internal_api/public/write_transaction.h

Index: sync/internal_api/public/write_transaction.h
diff --git a/sync/internal_api/public/write_transaction.h b/sync/internal_api/public/write_transaction.h
index df27cad62dd05a48b8d5815b37234bada90e7c18..661e8da6d5ef5023799e64a197170c0ebb5789cf 100644
--- a/sync/internal_api/public/write_transaction.h
+++ b/sync/internal_api/public/write_transaction.h
@@ -30,6 +30,11 @@ class WriteTransaction : public BaseTransaction {
   // Start a new read/write transaction.
   WriteTransaction(const tracked_objects::Location& from_here,
                    UserShare* share);
+  // |new_model_version| stores updated model version if model is changed by
+  // the transaction, or -1 if not after transaction is closed. This
+  // constructor is used for model types that support embassy data.
+  WriteTransaction(const tracked_objects::Location& from_here,
+                   UserShare* share, int64* new_model_version);
   virtual ~WriteTransaction();
 
   // Provide access to the syncable transaction from the API WriteNode.