### 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
#if defined(OS_WIN)
  
  
  base::ThreadRestrictions::ScopedAllowIO allow_io;
#endif
  scoped_refptr<printing::PrintBackend> print_backend =
      printing::PrintBackend::CreateInstance(
          g_browser_process->GetApplicationLocale());
  std::string printer_name;
  printing::mojom::ResultCode code =
      print_backend->GetDefaultPrinterName(printer_name);
  
  
  if (code != printing::mojom::ResultCode::kSuccess)
    LOG(ERROR) << "Failed to get default printer name";
  
  if (printer_name.empty()) {
    printing::PrinterList printers;
    if (print_backend->EnumeratePrinters(&printers) !=
        printing::mojom::ResultCode::kSuccess)
      return std::make_pair("Failed to enumerate printers", std::u16string());
    if (!printers.empty())
      printer_name = printers.front().printer_name;
  }
  return std::make_pair(std::string(), base::UTF8ToUTF16(printer_name));
}
scoped_refptr<base::TaskRunner> CreatePrinterHandlerTaskRunner() {