UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.90 Safari/537.36

Steps to reproduce the problem:
1. Create a simple HTM Lform that submits to a web server via a POST request
2. Have the web server return a simple page.
3. Visit the page with the HTML form on it.
4. Enter some data and hit submit.
5. See that the content-type header was correctly specified in the chrome developer tools.
6. Refresh the page, saying yes to allow the action to be repeated
7. Check in the chrome dev tools - the "content-type" is blank

What is the expected behavior?
The "content-type" header is correctly specified when refreshing the page.

What went wrong?
While the content-type header is indeed specified, the header in question has no content.

Did this work before? Yes a version or two ago

Does this work in other browsers? Yes

Chrome version: 60.0.3112.90  Channel: stable
OS Version: 10.0
Flash Version: 

Headers from the first request:

POST /public/account/verification/request HTTP/1.1
Host: some.host.name.tld
Connection: keep-alive
Content-Length: 26
Pragma: no-cache
Cache-Control: no-cache
Origin: https://some.host.name.tld
Upgrade-Insecure-Requests: 1
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.90 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Referer: https://some.host.name.tld/public/account/verification/request
Accept-Encoding: gzip, deflate, br
Accept-Language: en-GB,en-US;q=0.8,en;q=0.6
Cookie: PHPSESSID=xyzw

Headers from the refreshed request:

POST /public/account/verification/request HTTP/1.1
Host: some.host.name.tld
Connection: keep-alive
Content-Length: 26
Pragma: no-cache
Cache-Control: no-cache
Origin: https://some.host.name.tld
Upgrade-Insecure-Requests: 1
Content-Type:
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.90 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Referer: https://some.host.name.tld/public/account/verification/request
Accept-Encoding: gzip, deflate, br
Accept-Language: en-GB,en-US;q=0.8,en;q=0.6
Cookie: PHPSESSID=xyzw