UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.62 Safari/537.36

Steps to reproduce the problem:
1. Load any website with the network tab of dev tools open
2. Right click on any request and copy as fetch
3. Right click again and copy as curl
4. Notice that the curl request has more headers

What is the expected behavior?
The "copy as fetch" feature should properly emulate the fetch, just like the "copy as curl" feature.

What went wrong?
Here's an example request (with `body` and `url` changed to "foobar" to hide info):

fetch("http://example.com", {"credentials":"omit","headers":{},"referrer":"http://example.com","referrerPolicy":"no-referrer-when-downgrade","body":"foobar","method":"POST","mode":"cors"});

curl 'http://example.com' -H 'Origin: http://example.com' -H 'Accept-Encoding: gzip, deflate' -H 'Accept-Language: en-GB,en-US;q=0.9,en;q=0.8' -H 'User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.17 Safari/537.36' -H 'Content-Type: application/x-www-form-urlencoded; charset=UTF-8' -H 'Accept: */*' -H 'Referer: http://example.com' -H 'X-Requested-With: XMLHttpRequest' -H 'Connection: keep-alive' --data 'foobar' --compressed

The curl request worked fine, but I got an internal server error (500) for the `fetch` because it doesn't include this header: 'Content-Type: application/x-www-form-urlencoded; charset=UTF-8'

Did this work before? N/A 

Chrome version: 67.0.3396.62  Channel: n/a
OS Version: 16.04.04
Flash Version: