+void GCMStoreImpl::OverwriteOutgoingMessage(const std::string& persistent_id,
+ const MCSMessage& message,
+ const UpdateCallback& callback) {
+ DCHECK_EQ(message.tag(), kDataMessageStanzaTag);
+ std::string app_id = reinterpret_cast<const mcs_proto::DataMessageStanza*>(
+ &message.GetProtobuf())->category();
+ DCHECK(!app_id.empty());
+ // There should already be pending messages for this app.
+ DCHECK(app_message_counts_.count(app_id));
+ // TODO(zea): consider verifying the specific message already exists.
+ blocking_task_runner_->PostTask(
+ FROM_HERE,
+ base::Bind(&GCMStoreImpl::Backend::AddOutgoingMessage,
+ backend_,
+ persistent_id,
+ message,
+ callback));
+}
+