

### Preflight Checklist
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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
public:
  explicit FileURLLoaderFactory(int child_id) : child_id_(child_id) {}
 private:
  
  void CreateLoaderAndStart(
      mojo::PendingReceiver<network::mojom::URLLoader> loader,
      int32_t routing_id,
      int32_t request_id,
      uint32_t options,
      const network::ResourceRequest& request,
      mojo::PendingRemote<network::mojom::URLLoaderClient> client,
      const net::MutableNetworkTrafficAnnotationTag& traffic_annotation)
      override {
    if (!content::ChildProcessSecurityPolicy::GetInstance()->CanRequestURL(
            child_id_, request.url)) {
      mojo::Remote<network::mojom::URLLoaderClient>(std::move(client))
          ->OnComplete(
              network::URLLoaderCompletionStatus(net::ERR_ACCESS_DENIED));
      return;
    }
    content::CreateFileURLLoaderBypassingSecurityChecks(
        request, std::move(loader), std::move(client),
        nullptr,
         true);
  }
  void Clone(