calling ap_get_brigade with nonempty brigade

[Joe Schaefer]

ap_http_filter seems to assume it will receive an empty 
brigade from its caller. The problem is around lines 
1028 - 1035 in http_protocol.c:

    rv = ap_get_brigade(f->next, b, mode, block, readbytes);

    if (rv != APR_SUCCESS) {
        return rv;
    }

    /* How many bytes did we just read? */
    apr_brigade_length(b, 0, &totalread);

totalread is only accurate in this context if b was 
empty to begin with.  Is this is a bug in ap_http_filter?

-- 
Joe Schaefer