Estou usando a API HtmlUnit para adicionar suporte ao rastreador ao meu aplicativo GWT da seguinte forma:

PrintWriter out = null;
try {
    resp.setCharacterEncoding(CHAR_ENCODING);
    resp.setContentType("text/html");

    url = buildUrl(req);
    out = resp.getWriter();

    WebClient webClient = webClientProvider.get();

    // set options
    WebClientOptions options = webClient.getOptions();
    options.setCssEnabled(false);
    options.setThrowExceptionOnScriptError(false);
    options.setThrowExceptionOnFailingStatusCode(false);
    options.setRedirectEnabled(true);
    options.setJavaScriptEnabled(true);

    // set timeouts
    webClient.setJavaScriptTimeout(0);
    webClient.waitForBackgroundJavaScript(20000);

    // ajax controller
    webClient.setAjaxController(new NicelyResynchronizingAjaxController());

    // render page
    HtmlPage page = webClient.getPage(url);

    webClient.getJavaScriptEngine().pumpEventLoop(timeoutMillis);

    out.println(page.asXml());

    webClient.closeAllWindows();
}
...

Contudo; somente a página do host HTML para meu aplicativo GWT é produzida e enviada ao cliente.

ATUALIZAR: Aqui está a saída do Chrome DevTools:

Request URL:http://127.0.0.1:8888/MyApp.html?gwt.codesvr=127.0.0.1:9997&_escaped_fragment_=myobject%3Bid%3D507ac730e4b0e3b7a73b1b81
Request Method:GET
Status Code:200 OK
Request Headersview source
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Charset:ISO-8859-1,utf-8;q=0.7,*;q=0.3
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-GB,en-US;q=0.8,en;q=0.6
Cache-Control:max-age=0
Connection:keep-alive
Cookie:__utma=96992031.428505342.1351707614.1351707614.1356355174.2; __utmb=96992031.1.10.1356355174; __utmc=96992031; __utmz=96992031.1351707614.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)
Host:127.0.0.1:8888
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11
Query String Parametersview URL encoded
gwt.codesvr:127.0.0.1:9997
_escaped_fragment_:myobject;id=507ac730e4b0e3b7a73b1b81
Response Headersview source
Content-Type:text/html; charset=utf-8
Server:Jetty(6.1.x)
Transfer-Encoding:chunked

Por que o código do GWT não está sendo executado?