Find mime from file extension if the mime is empty

     */

    private void downloadStart(String url, String userAgent,

            String contentDisposition, String mimeType, long contentLength) {

        // This will only work if the url ends with the filename

        if (mimeType.isEmpty()) {

            try {

                String extension = url.substring(url.lastIndexOf('.') + 1);

                mimeType = libcore.net.MimeUtils.guessMimeTypeFromExtension(extension);

                // MimeUtils might return null, not sure if downloadmanager is happy with that

                if (mimeType == null)

                    mimeType = "";

            } catch(IndexOutOfBoundsException exception) {

                // mimeType string end with a '.', not much to do

            }

        }

        mimeType = MimeTypeMap.getSingleton().remapGenericMimeType(

                mimeType, url, contentDisposition);

        mCallbackProxy.onDownloadStart(url, userAgent,