### Preflight Checklist
<!-- Please ensure you've completed the following steps by replacing [ ] with [x]-->

* [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.

Ref #19447

### Issue Details

* **Electron Version:**
  * 9.0.0-beta.24
* **Operating System:**
  * macOS 10.15, Windows 10
* **Last Known Working Electron version:**
  * none

### Expected Behavior
`e.sender` object received from an extension background page should have `webPreferences` and `session` initialized. It looks like `options` in `api::WebContents` constructor don't get initialized properly for an extension background page.

### Actual Behavior
`e.sender` object doesn't have `session` and `e.sender.getWebPreferences()` returns `null`.

### To Reproduce
https://github.com/sentialx/electron-quick-start/tree/extensions/no-session

Just run it and you will see something like this:
![image](https://user-images.githubusercontent.com/11065386/82097607-82994400-9703-11ea-8291-0eb987d8aca0.png)

### Additional Information
This is a real blocker for anyone who would want to provide own `chrome` APIs in background pages initialized from different sessions.
shell/browser/api/electron_api_web_contents.cc
content::RenderFrameHost* render_frame_host,
    const GURL& security_origin,
    blink::mojom::MediaStreamType type) {
  auto* ontents =
      content::Ws::FromRenderFrameHost(render_frame_host);
  auto* permission_helper =
      WsPermissionHelper::FromWs(ontents);
  return permission_helper->CheckMediaAccessPermission(security_origin, type);
}
void Ws::RequestMediaAccessPermission(
    content::Ws* ontents,
    const content::MediaStreamRequest& request,
    content::MediaResponseCallback callback) {
  auto* permission_helper =
      WsPermissionHelper::FromWs(ontents);
  permission_helper->RequestMediaAccessPermission(request, std::move(callback));
}
void Ws::RequestToLockMouse(content::Ws* ontents,
                                     bool user_gesture,
                                     bool last_unlocked_by_target) {
  auto* permission_helper =
      WsPermissionHelper::FromWs(ontents);
  permission_helper->RequestPointerLockPermission(user_gesture);
}
std::unique_ptr<content::BluetoothChooser> Ws::RunBluetoothChooser(
    content::RenderFrameHost* frame,
    const content::BluetoothChooser::EventHandler& event_handler) {
  return std::make_unique<BluetoothChooser>(this, event_handler);
}
content::JavaScriptDialogManager* Ws::GetJavaScriptDialogManager(