IFRAME is not handled as atomic token

[radubarbos]

If the IFRAME is splitted in 2 writes like:
document.write('<IFRAME SRC="...">');
document.write('</IFRAME>');
then it's not treated as an atomic token but the first write as start tag which is not fine.
An side effect is that the 'done' write function is not executed and the active stream is not reset.

The solution I found working is adding the iframe check to the peekTokenImpl function
like:
if (token.type === 'startTag' && /script|style|iframe/i.test(token.tagName)) {
return null;
}