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..6a369638b65674983913f58b8b43456dd2959112 100644
--- a/sync/syncable/write_transaction.h
+++ b/sync/syncable/write_transaction.h
@@ -11,12 +11,22 @@
 namespace syncer {
 namespace syncable {
 
+extern const int64 kInvalidTransactionVersion;
+
 // Locks db in constructor, unlocks in destructor.
 class WriteTransaction : public BaseTransaction {
  public:
   WriteTransaction(const tracked_objects::Location& from_here,
                    WriterTag writer, Directory* directory);
 
+  // Constructor used for getting back transaction version after making sync
+  // API changes to one model. If model is changed by the transaction,
+  // the new transaction version of the model and modified nodes will be saved
+  // in |transaction_version| upon destruction of the transaction. If model is
+  // not changed,  |transaction_version| will be kInvalidTransactionVersion.
+  WriteTransaction(const tracked_objects::Location& from_here,
+                   Directory* directory, int64* transaction_version);
+
   virtual ~WriteTransaction();
 
   void SaveOriginal(const EntryKernel* entry);
@@ -36,10 +46,18 @@ 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_;
 
+  // Stores new transaction version of changed model and nodes if model is
+  // indeed changed. kInvalidTransactionVersion otherwise. Not owned.
+  int64* transaction_version_;
+
   DISALLOW_COPY_AND_ASSIGN(WriteTransaction);
 };