### Preflight Checklist
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* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### 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
#include "services/network/public/cpp/simple_url_loader.h"
#include "services/network/public/mojom/chunked_data_pipe_getter.mojom.h"
#include "services/network/public/mojom/url_loader_factory.mojom.h"
#include "shell/browser/api/electron_api_session.h"
#include "shell/browser/electron_browser_context.h"
#include "shell/common/gin_converters/callback_converter.h"
#include "shell/common/gin_converters/gurl_converter.h"
#include "shell/common/gin_converters/net_converter.h"
#include "shell/common/gin_helper/dictionary.h"
#include "shell/common/gin_helper/object_template_builder.h"
#include "shell/common/node_includes.h"
namespace gin {
template <>
struct Converter<network::mojom::HttpRawHeaderPairPtr> {
  static v8::Local<v8::Value> ToV8(
      v8::Isolate* isolate,
      const network::mojom::HttpRawHeaderPairPtr& pair) {
    gin_helper::Dictionary dict = gin::Dictionary::CreateEmpty(isolate);
    dict.Set("key", base::ToLowerASCII(pair->key));
    dict.Set("value", pair->value);
    return dict.GetHandle();
  }
};
}  
namespace electron {
namespace api {
namespace {
class BufferDataSource : public mojo::DataPipeProducer::DataSource {
 public:
  explicit BufferDataSource(base::span<char> buffer) {