if (ProcessCanceledCase(aChannel)) return NS_OK;
NS_IMETHODIMP nsDocumentOpenInfo::OnStartRequest(nsIChannel * aChannel, nsISupports * aCtxt){  nsresult rv;  //  // Deal with "special" HTTP responses:  //  // - In the case of a 204 (No Content) response, do not try to find a  //   content handler.  Just return.  This causes the request to be  //   ignored.  //  nsCOMPtr<nsIHTTPChannel> httpChannel(do_QueryInterface(aChannel, &rv));  if (NS_SUCCEEDED(rv)) {    PRUint32 responseCode = 0;    httpChannel->GetResponseStatus(&responseCode);    if (204 == responseCode) {      return NS_OK;    }  }  rv = DispatchContent(aChannel, aCtxt);  if (m_targetStreamListener)    rv = m_targetStreamListener->OnStartRequest(aChannel, aCtxt);  return rv;}