@Override
        public Response process(Request request, Execution execution) {
            Response response = execution.process(request);
            // TODO: Consider for to best provide helpers for this
            response.data().addDataListener(new RunnableExecution(request,
                                                                  new ExecutionWithResponse(streamChain, response, execution)));
            return response;
        }
Registers a chain to be invoked each time new data becomes available in the first child list
container-core/src/test/java/com/yahoo/processing/test/ProcessorLibrary.java