

### 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
command_line->AppendSwitchNative(switches::kAppUserModelId,
                                       current_app_id);
      CoTaskMemFree(current_app_id);
    }
#endif
    if (delegate_) {
      auto app_path = static_cast<api::App*>(delegate_)->GetAppPath();
      command_line->AppendSwitchPath(switches::kAppPath, app_path);
    }
    content::WebContents* web_contents =
        GetWebContentsFromProcessID(process_id);
    if (web_contents) {
      auto* web_preferences = WebContentsPreferences::From(web_contents);
      if (web_preferences)
        web_preferences->AppendCommandLineSwitches(
            command_line, IsRendererSubFrame(process_id));
      auto preloads = SessionPreferences::GetValidPreloads(
          web_contents->GetBrowserContext());
      if (!preloads.empty())
        command_line->AppendSwitchNative(
            switches::kPreloadScripts,
            base::JoinString(preloads, kPathDelimiter));
      if (CanUseCustomSiteInstance()) {
        command_line->AppendSwitch(
            switches::kDisableElectronSiteInstanceOverrides);
      }
    }
  }
}
void ElectronBrowserClient::DidCreatePpapiPlugin(