Implement a bag of chips for sync.

sync/engine/syncer_proto_util.h

Index: sync/engine/syncer_proto_util.h
diff --git a/sync/engine/syncer_proto_util.h b/sync/engine/syncer_proto_util.h
index b674b50c320c9934ef65587d7d31fed18d9a37b4..fab140649412523997ca31134bfe77d53658322a 100644
--- a/sync/engine/syncer_proto_util.h
+++ b/sync/engine/syncer_proto_util.h
@@ -74,6 +74,11 @@ class SyncerProtoUtil {
   static const std::string& NameFromCommitEntryResponse(
       const sync_pb::CommitResponse_EntryResponse& entry);
 
+  // Persist the bag of chips if it is present in the response.
+  static void PersistBagOfChips(
+      syncable::Directory* dir,
+      const sync_pb::ClientToServerResponse& response);
+
   // EntitySpecifics is used as a filter for the GetUpdates message to tell
   // the server which datatypes to send back.  This adds a datatype so that
   // it's included in the filter.
@@ -92,6 +97,11 @@ class SyncerProtoUtil {
   static void AddRequestBirthday(syncable::Directory* dir,
                                  sync_pb::ClientToServerMessage* msg);
 
+  // Pull the bag of chips from the dir and put it into the msg.
+  static void AddBagOfChips(syncable::Directory* dir,
+                            sync_pb::ClientToServerMessage* msg);
+
+
   // Set the protocol version field in the outgoing message.
   static void SetProtocolVersion(sync_pb::ClientToServerMessage* msg);