response header does not include all the properties

[jliu1970]

Description

Send a post request through Iron-ajax. at the function to handle response, I have the code
onResponse: function (e, request) {
var headers = request.xhr.getAllResponseHeaders();
alert(headers)
}

Expected outcome

I was expecting to see a json object below (as I see when I post the same request through swagger-ui provided by the server):
{
"date": "Mon, 04 Mar 2019 21:09:12 GMT",
"validationerror": "Validation Failed for Agency Group",
"transfer-encoding": "chunked",
"access-control-allow-methods": "POST, GET, OPTIONS, PUT, DELETE",
"content-type": "application/json;charset=UTF-8",
"access-control-allow-origin": "https://************",
"access-control-max-age": "3600",
"access-control-allow-credentials": "true",
"access-control-allow-headers": "Content-Type, Accept, Access-Control-Allow-Headers, Authorization, X-Requested-With",
"server": "nginx/1.15.6",
"request-context": "appId="
}

Actual outcome

I only saw:
"content-type": "application/json;charset=UTF-8",

Live Demo

Steps to reproduce

Browsers Affected

• [x ] Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10