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

sync/syncable/write_transaction.h

Index: sync/syncable/write_transaction.h
diff --git a/sync/syncable/write_transaction.h b/sync/syncable/write_transaction.h
index 17264c4c65e3c883439ca84f202c7d1e5b0af24a..aa0ae8346dbff219bce5d256d594eff34346346f 100644
--- a/sync/syncable/write_transaction.h
+++ b/sync/syncable/write_transaction.h
@@ -36,6 +36,10 @@ class WriteTransaction : public BaseTransaction {
   ModelTypeSet NotifyTransactionChangingAndEnding(
       const ImmutableEntryKernelMutationMap& mutations);
 
+  // Increment versions of the models whose entries are modified and set the
+  // version on the changed entries.
+  void UpdateTransactionVersion(const std::vector<int64>& entry_changed);
+
   // Only the original fields are filled in until |RecordMutations()|.
   // We use a mutation map instead of a kernel set to avoid copying.
   EntryKernelMutationMap mutations_;