in src/main/java/org/apache/sling/api/servlets/SlingSafeMethodsServlet.java [171:205]
    protected void doTrace(@NotNull SlingHttpServletRequest request,
            @NotNull SlingHttpServletResponse response) throws ServletException,
            IOException {
        String CRLF = "\r\n";
        StringBuffer responseString = new StringBuffer();
        responseString.append("TRACE ").append(request.getRequestURI());
        responseString.append(' ').append(request.getProtocol());
        Enumeration<?> reqHeaderEnum = request.getHeaderNames();
        while (reqHeaderEnum.hasMoreElements()) {
            String headerName = (String) reqHeaderEnum.nextElement();
            Enumeration<?> reqHeaderValEnum = request.getHeaders(headerName);
            while (reqHeaderValEnum.hasMoreElements()) {
                responseString.append(CRLF);
                responseString.append(headerName).append(": ");
                responseString.append(reqHeaderValEnum.nextElement());
            }
        }
        responseString.append(CRLF);
        String charset = "UTF-8";
        byte[] rawResponse = responseString.toString().getBytes(charset);
        int responseLength = rawResponse.length;
        response.setContentType("message/http");
        response.setCharacterEncoding(charset);
        response.setContentLength(responseLength);
        ServletOutputStream out = response.getOutputStream();
        out.write(rawResponse);
    }