Setting onreadystatechange / onload after send() is called results in Zone not completing

[matthewp]

Example code:

var xhr = new XMLHttpRequest();
xhr.open("GET", "http://chat.donejs.com/api/messages");
xhr.send();
xhr.onreadystatechange = function(){
	if(xhr.readyState === 4) {
		zone.data.worked = true;
	}
};