Implement a bag of chips for sync.

sync/engine/build_commit_command.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sync/engine/build_commit_command.h"
 
 #include <limits>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 96 matching lines @@
   commit_message_->set_share(session->context()->account_name());
   commit_message_->set_message_contents(sync_pb::ClientToServerMessage::COMMIT);
 
   sync_pb::CommitMessage* commit_message = commit_message_->mutable_commit();
   commit_message->set_cache_guid(
       session->write_transaction()->directory()->cache_guid());
   AddExtensionsActivityToMessage(session, commit_message);
   SyncerProtoUtil::SetProtocolVersion(commit_message_);
   SyncerProtoUtil::AddRequestBirthday(
       session->write_transaction()->directory(), commit_message_);
+  SyncerProtoUtil::AddBagOfChips(
+      session->write_transaction()->directory(), commit_message_);
 
   // Cache previously computed position values.  Because |commit_ids|
   // is already in sibling order, we should always hit this map after
   // the first sibling in a consecutive run of commit items.  The
   // entries in this map are (low, high) values describing the
   // space of positions that are immediate successors of the item
   // whose ID is the map's key.
   std::map<Id, std::pair<int64, int64> > position_map;
 
   for (size_t i = 0; i < batch_commit_set_.Size(); i++) {
@@ skipping 131 matching lines @@
   if (delta <= static_cast<uint64>(GetGap()*2))
     return lo + (static_cast<int64>(delta) + 7) / 8;  // Interpolate.
   else if (lo == GetFirstPosition())
     return hi - GetGap();  // Extend range just before successor.
   else
     return lo + GetGap();  // Use or extend range just after predecessor.
 }
 
 
 }  // namespace syncer