

### 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.

### Issue Details

* **Electron Version:**
  * Tested with 8.0.0 and v9.0.0-beta.1
* **Operating System:**
  * macOS 10.15.3 (19D76)
* **Last Known Working Electron version:**
  * 7.1.12

### Expected Behavior

`navigator.mediaDevices.enumerateDevices()` should return a list of MediaDevices with a `label` and a `deviceId` property. The `deviceId` property should stay the same across reloads and restarts.

### Actual Behavior
The `deviceId` property changes with every reload/restart.

### To Reproduce
Simply execute `navigator.mediaDevices.enumerateDevices()` in the renderer process and compare the ids of the media devices to a different execution.

See this fork for an example:
https://github.com/codedrift/electron-quick-start

```sh
$ git clone https://github.com/codedrift/electron-quick-start -b media-device-ids
$ npm install
$ npm start || electron .
```

### Additional Information
It seems to work fine in a regular Chrome 80 browser. 

shell/browser/electron_browser_client.cc
const GURL& url,
    content::WebContents::OnceGetter web_contents_getter,
    int child_id,
    content::NavigationUIData* navigation_data,
    bool is_main_frame,
    ui::PageTransition page_transition,
    bool has_user_gesture,
    const base::Optional<url::Origin>& initiating_origin,
    mojo::PendingRemote<network::mojom::URLLoaderFactory>* out_factory) {
  base::PostTask(
      FROM_HERE, {BrowserThread::UI},
      base::BindOnce(&HandleExternalProtocolInUI, url,
                     std::move(web_contents_getter), has_user_gesture));
  return true;
}
std::vector<std::unique_ptr<content::NavigationThrottle>>
ElectronBrowserClient::CreateThrottlesForNavigation(
    content::NavigationHandle* handle) {
  std::vector<std::unique_ptr<content::NavigationThrottle>> throttles;
  throttles.push_back(std::make_unique<ElectronNavigationThrottle>(handle));
#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
  throttles.push_back(
      std::make_unique<extensions::ExtensionNavigationThrottle>(handle));
#endif
  return throttles;
}
content::MediaObserver* ElectronBrowserClient::GetMediaObserver() {