Unfortunately for Chromium's DevTools for some filed or blocked requests shows you:
What we recommend to do is open Terminal and write
curl command which reproduces the request:
curl -H "Origin: http://example.com" \ -H "Access-Control-Request-Method: POST" \ -H "Access-Control-Request-Headers: X-Requested-With" \ -X OPTIONS --verbose \ https://www.googleapis.com/discovery/v1/apis?fields=
Carefully define headers by coping them from Request in DevTools. Also you can use Postman instead of curl.