This is an issue distinct to Chrome, but there are two paths you can take to fix it.
I noticed the error once I added this specific header to my PHP script.
header('Content-Type: application/json');
The error appears to be related to PHP sessions when sending response headers. So according to chromium bug report 424599, this was fixed and you can just update to a newer version of Chrome. But if for some reason you can't or don't want to update, the workaround would be to remove these response headers from your PHP script if possible (that's what I did because it wasn't required).