BlockingHandler doesn't report content-length if it fills more than one buffer

    public static void main(String[] args) {
        HttpHandler handler = exchange -> {
            int size = Integer.parseInt(exchange.getQueryParameters().get("size").getFirst());
            String data = String.format("%0" + size + "d", 0).replace('0', '-');
            exchange.getResponseSender().send(data);
        };

        EncodingHandler gzipHandler = new EncodingHandler(new ContentEncodingRepository()
                .addEncodingHandler("gzip",
                    // This 1000 is a priority, not exactly sure what it does.
                    new GzipEncodingProvider(), 1000,
                    // Anything under a content-length of 20 will not be gzipped
                    Predicates.maxContentSize(20)))
                .setNext(handler);

        BlockingHandler blockingHandler = new BlockingHandler();
        blockingHandler.setRootHandler(gzipHandler);

        Undertow.builder()
                .addHttpListener(8080, "0.0.0.0", blockingHandler)
                .build().start();
    }

curl -v -s -H 'Accept-Encoding: gzip' -o /dev/null http://localhost:8080/?size=16383
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8080 (#0)
> GET /?size=16383 HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.51.0
> Accept: */*
> Accept-Encoding: gzip
>
< HTTP/1.1 200 OK
< Content-Encoding: gzip
< Connection: keep-alive
< Content-Length: 52
< Date: Tue, 14 Nov 2017 03:48:31 GMT

curl -v -s -H 'Accept-Encoding: gzip' -o /dev/null http://localhost:8080/?size=16384
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8080 (#0)
> GET /?size=16384 HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.51.0
> Accept: */*
> Accept-Encoding: gzip
>
< HTTP/1.1 200 OK
< Connection: keep-alive
< Transfer-Encoding: chunked
< Date: Tue, 14 Nov 2017 03:48:50 GMT