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

sync/internal_api/public/base_transaction.h

Index: sync/internal_api/public/base_transaction.h
diff --git a/sync/internal_api/public/base_transaction.h b/sync/internal_api/public/base_transaction.h
index 242a6b93545780d0cd96d4ced7d9ef64e5d2af67..10debfe9c7dfb6581d4c5c76ff7453ea0e6dbaad 100644
--- a/sync/internal_api/public/base_transaction.h
+++ b/sync/internal_api/public/base_transaction.h
@@ -35,6 +35,10 @@ class BaseTransaction {
     return directory_;
   }
 
+  // Return |transaction_version| of |type| stored in sync directory's
+  // persisted info.
+  int64 GetModelVersion(ModelType type);
+
  protected:
   explicit BaseTransaction(UserShare* share);
   virtual ~BaseTransaction();