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### Issue Details

* **Electron Version:**
  8.0.1
* **Operating System:**
  macOS 10.14.6

### Expected Behavior
Send a request with `referer` header. It's worked with Node's `http/https` module, but failed when I change to `net.request`.

### Actual Behavior
No referer header

### To Reproduce
```js
ses.protocol.interceptStreamProtocol("https", (request, callback) => {
	const resp = sendRequestWithNetRequest({
       url: request.url,
       method: request.method,
	   headers: {
			...request.headers,
			referer: request.referrer  // only referrer has been ignored!!
       }
    })
    callback({
        data: resp.body,
        statusCode: resp.statusCode,
        headers: resp.headers
      });
});
```

shell/browser/api/electron_api_url_loader.cc
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_;
  bool is_writing_ = false;
  uint64_t bytes_written_ = 0;