### 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
return ontents()->GetController().CanGoToOffset(offset);
}
void WebContents::GoToOffset(int offset) {
  if (CanGoToOffset(offset))
    ontents()->GetController().GoToOffset(offset);
}
bool WebContents::CanGoToIndex(int index) const {
  return index >= 0 && index < GetHistoryLength();
}
void WebContents::GoToIndex(int index) {
  if (CanGoToIndex(index))
    ontents()->GetController().GoToIndex(index);
}
int WebContents::GetActiveIndex() const {
  return ontents()->GetController().GetCurrentEntryIndex();
}
void WebContents::ClearHistory() {
   In some rare cases (normally while there is no real history) we are in a
   state where we can't prune navigation entries
  if (ontents()->GetController().CanPruneAllButLastCommitted()) {
    ontents()->GetController().PruneAllButLastCommitted();
  }
}
int WebContents::GetHistoryLength() const {
  return ontents()->GetController().GetEntryCount();
}
const std::string WebContents::GetWebRTCIPHandlingPolicy() const {
  return ontents()->GetMutableRendererPrefs()->webrtc_ip_handling_policy;
}
void WebContents::SetWebRTCIPHandlingPolicy(