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..0af308dcae37314213a4f319a84bc8a060fe81fb 100644
--- a/sync/syncable/write_transaction.h
+++ b/sync/syncable/write_transaction.h
@@ -17,6 +17,12 @@ class WriteTransaction : public BaseTransaction {
   WriteTransaction(const tracked_objects::Location& from_here,
                    WriterTag writer, Directory* directory);
 
+  // Constructor used for getting back model version after making sync
+  // API changes to one model. During destruction, |new_model_version| stores
+  // the new model version if model is changed, or -1 if model is not changed.
+  WriteTransaction(const tracked_objects::Location& from_here,
+                   Directory* directory, int64* new_model_version);
+
   virtual ~WriteTransaction();
 
   void SaveOriginal(const EntryKernel* entry);
@@ -36,10 +42,17 @@ 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_;
 
+  // Not owned.
+  int64* new_model_version_;
+
   DISALLOW_COPY_AND_ASSIGN(WriteTransaction);
 };