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### 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
ElectronBrowserClient::GetServiceManifestOverlay(base::StringPiece name) {
  if (name == content::mojom::kBrowserServiceName)
    return GetElectronContentBrowserOverlayManifest();
  return base::nullopt;
}
std::unique_ptr<content::BrowserMainParts>
ElectronBrowserClient::CreateBrowserMainParts(
    const content::MainFunctionParams& params) {
  return std::make_unique<ElectronBrowserMainParts>(params);
}
void ElectronBrowserClient::WebNotificationAllowed(
    int render_process_id,
    base::OnceCallback<void(bool, bool)> callback) {
  content::WebContents* web_contents =
      WebContentsPreferences::GetWebContentsFromProcessID(render_process_id);
  if (!web_contents) {
    std::move(callback).Run(false, false);
    return;
  }
  auto* permission_helper =
      WebContentsPermissionHelper::FromWebContents(web_contents);
  if (!permission_helper) {
    std::move(callback).Run(false, false);
    return;
  }
  permission_helper->RequestWebNotificationPermission(
      base::BindOnce(std::move(callback), web_contents->IsAudioMuted()));
}
void ElectronBrowserClient::RenderProcessHostDestroyed(