[fetch] POST calls - Request Payload is not shown with native fetch (#59)

```
fetch(url, {
  method: 'post',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    id: 'Hubot',
    name: 'hubot',
  })
})
```

The payload body is not shown on both Chrome and Firefox Dev tools. Tried even with Canary and Nightly builds.

However, the Github Fetch polyfill is properly showing the payload data. 

---
Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/59