### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/main/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/main/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

14.0.1

### What operating system are you using?

macOS

### Operating System Version

macOS Big Sur 11.6.1

### What arch are you using?

x64

### Last Known Working Electron version

14.0.0

### Expected Behavior


When `BrowserView.setBackgroundColor` is called with an explicit color, expect the background to be the color selected.

When `BrowserView.setBackgroundColor` is not called, expect the background of the `BrowserView` to be transparent by default; and can see through `BrowserWindow`'s background color.



### Actual Behavior

The `BrowserView` background is always white.

### Testcase Gist URL

https://gist.github.com/kevinlinv/2de60478ffec6a2f18f1ec0fc6f5add9

### Additional Information

Here is a quick recording that reproduces the error.

https://user-images.githubusercontent.com/44967897/140694174-e27aff28-1847-4813-bc46-d9fda6569128.mp4


shell/browser/api/electron_api_web_contents.cc
content::RenderFrameHost* render_frame_host) {
  HandleNewRenderFrame(render_frame_host);
  
  
  
  
  
  auto* rfh_impl =
      static_cast<content::RenderFrameHostImpl*>(render_frame_host);
  if (rfh_impl->lifecycle_state() ==
      content::RenderFrameHostImpl::LifecycleStateImpl::kSpeculative) {
    return;
  }
  content::RenderFrameHost::LifecycleState lifecycle_state =
      render_frame_host->GetLifecycleState();
  if (lifecycle_state == content::RenderFrameHost::LifecycleState::kActive) {
    v8::Isolate* isolate = JavascriptEnvironment::GetIsolate();
    v8::HandleScope handle_scope(isolate);
    gin_helper::Dictionary details =
        gin_helper::Dictionary::CreateEmpty(isolate);
    details.SetGetter("frame", render_frame_host);
    Emit("frame-created", details);
  }
}
void WebContents::RenderFrameDeleted(