It's a crappy hack, but paste this into your JavaScript console:

    function exportFile(path) { var b = new Blob([FS.readFile(path).buffer], {'type': 'text/plain'}); var u = URL.createObjectURL(b); window.location.href = u; }

And then you can run this to export files:

    exportFile("/usr/local/share/vim/vimrc");