Some headers like
Connection are forbidden to be changed programmatically, i.e. in AJAX requests, see https://developer.mozilla.org/en-US/docs/Glossary/Forbidden_header_name for more info.
Is anything broken on the site you are looking at that you are debugging? It looks like you have devtools open on Gmail or some other Google property.
I’m pretty sure it was on Google Drive
OK. Best to use Google’s feedback system if something does not work in their web products.