### 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
int bottom = 0;
      margins.Get("bottom", &bottom);
      custom_margins.SetIntKey(printing::kSettingMarginBottom, bottom);
      int left = 0;
      margins.Get("left", &left);
      custom_margins.SetIntKey(printing::kSettingMarginLeft, left);
      int right = 0;
      margins.Get("right", &right);
      custom_margins.SetIntKey(printing::kSettingMarginRight, right);
      settings.SetPath(printing::kSettingMarginsCustom,
                       std::move(custom_margins));
    }
  } else {
    settings.SetIntKey(
        printing::kSettingMarginsType,
        static_cast<int>(printing::mojom::MarginType::kDefaultMargins));
  }
   Set whether to print color or greyscale
  bool print_color = true;
  options.Get("color", &print_color);
  auto const color_model = print_color ? printing::mojom::ColorModel::kColor
                                       : printing::mojom::ColorModel::kGray;
  settings.SetIntKey(printing::kSettingColor, static_cast<int>(color_model));
   Is the orientation landscape or portrait.
  bool landscape = false;
  options.Get("landscape", &landscape);
  settings.SetBoolKey(printing::kSettingLandscape, landscape);
   We set the default to the system's default printer and only update
   if at the Chromium level if the user overrides.
   Printer device name as opened by the OS.