header added using an EventNotifier is not present at AggregationStrategy for http endpoints

public class ExchangeSentEventNotifier extends EventNotifierSupport {

	@Override
	protected void doStart() throws Exception {
        /*
         *  filter out unwanted events
         *  we are interested only in ExchangeSentEvent
         */
        setIgnoreCamelContextEvents(true);
        setIgnoreServiceEvents(true);
        setIgnoreRouteEvents(true);
        setIgnoreExchangeCreatedEvent(true);
        setIgnoreExchangeCompletedEvent(true);
        setIgnoreExchangeFailedEvents(true);
        setIgnoreExchangeSentEvents(false);		
	}

	@Override
	protected void doStop() throws Exception {

	}

	@Override
	public boolean isEnabled(EventObject event) {
		return event instanceof ExchangeSentEvent;
	}

	@Override
	public void notify(EventObject event) throws Exception {
    	if(event.getClass() == ExchangeSentEvent.class){
            ExchangeSentEvent eventSent = (ExchangeSentEvent)event;
            
            log.debug("Took " + eventSent.getTimeTaken() + " millis to send to: " + eventSent.getEndpoint());

            //storing time taken to the custom header            
            eventSent.getExchange().getIn().setHeader("x-time-taken", eventSent.getTimeTaken());
            
    	}
		
	}

}