* Electron version: 1.6.2
* Operating system: macOS 10.12

### Expected behavior

Requests sent with the net module should behave one of two ways regarding cookies.
- Either not care about cookies at all, and neither store them nor send them back automatically.
- Or, fully handle cookies, store them when getting a `set-cookie` header, and send them back when necessary, automatically (with the possibility of an option to disable this behaviour)

### Actual behavior

Requests sent with the net module store cookies in the Session used by the request when getting a `set-cookie` header, but do not send them back afterwards.

### How to reproduce

```bash
git clone https://github.com/arantes555/electron-net-cookies-testcase.git && cd electron-net-cookies-testcase
npm i
npm start
```
output: 
```
Server started
REQUEST-HEADERS { 'Accept-Encoding': 'gzip, deflate',
  'Accept-Language': 'fr',
  'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Electron/1.6.2 Safari/537.36' }
Response SET-COOKIE: undefined
STORED COOKIES: []
REQUEST-HEADERS { 'Accept-Encoding': 'gzip, deflate',
  'Accept-Language': 'fr',
  'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Electron/1.6.2 Safari/537.36' }
Response SET-COOKIE: a=1,b=1
STORED COOKIES: [{"name":"a","value":"1","domain":"localhost"},{"name":"b","value":"1","domain":"localhost"}]
REQUEST-HEADERS { 'Accept-Encoding': 'gzip, deflate',
  'Accept-Language': 'fr',
  'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Electron/1.6.2 Safari/537.36' }
Response SET-COOKIE: a=1,b=1
```

Btw, if I'm reporting multiple issues with the net module these days, it's because I'm working on https://github.com/arantes555/electron-fetch , if you wanna take a look :)
shell/browser/api/electron_api_url_loader.cc
return handle;
  }
  void OnWriteChunkComplete(gin_helper::Promise<void> promise,
                            MojoResult result) {
    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
    is_writing_ = false;
    if (result == MOJO_RESULT_OK) {
      promise.Resolve();
    } else {
      promise.RejectWithErrorMessage("mojo result not ok");
      Finished();
    }
  }
  
  
  void Done() {
    if (size_callback_) {
      std::move(size_callback_).Run(net::OK, bytes_written_);
      Finished();
    }
  }
  void Finished() {
    size_callback_.Reset();
    body_func_.Reset();
    receiver_.reset();
    data_producer_.reset();
  }
  GetSizeCallback size_callback_;
  mojo::Receiver<network::mojom::ChunkedDataPipeGetter> receiver_{this};
  std::unique_ptr<mojo::DataPipeProducer> data_producer_;