### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/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

14.0.0-beta.12

### What operating system are you using?

Windows

### Operating System Version

10.0.19042 Build 19042

### What arch are you using?

x64

### Last Known Working Electron version

13

### Expected Behavior

Window should be transparent

### Actual Behavior

Open a window with transparency enabled and delete the dom, the window will be white instead of transparent.
**Also seems like settings the backgroundColor property has no longer an effect.** I always see a white window

```
const {app, BrowserWindow} = require('electron')
const path = require("path");

function createWindow () {
	const mainWindow = new BrowserWindow({
		transparent: true,
		frame: false,
	})

	mainWindow.loadURL('https://example.com')
	mainWindow.webContents.openDevTools()
}

app.whenReady().then(createWindow)
```

### Testcase Gist URL

https://gist.github.com/e124340107f6c4a3ade8b36d98a16b9a

### Additional Information

_No response_
shell/browser/api/electron_api_web_contents.cc
ElectronBrowserContext* browser_context,
                                      bool is_guest) {
  browser_context_ = browser_context;
  ontents->SetDelegate(this);
#if BUILDFLAG(ENABLE_PRINTING)
  PrintPreviewMessageHandler::CreateForWebContents(ontents);
  PrintViewManagerElectron::CreateForWebContents(ontents);
  printing::CreateCompositeClientIfNeeded(ontents,
                                          browser_context->GetUserAgent());
#endif
#if BUILDFLAG(ENABLE_PDF_VIEWER)
  pdf::PDFWebContentsHelper::CreateForWebContentsWithClient(
      ontents, std::make_unique<ElectronPDFWebContentsHelperClient>());
#endif
  
  auto* web_preferences = WebContentsPreferences::From(ontents);
  offscreen_ =
      web_preferences && web_preferences->IsEnabled(options::kOffscreen);
  
  inspectable_ontents_ = std::make_unique<InspectableWebContents>(
      ontents, browser_context->prefs(), is_guest);
  inspectable_ontents_->SetDelegate(this);
  if (web_preferences) {
    std::string color_name;
    if (web_preferences->GetPreference(options::kBackgroundColor,
                                       &color_name)) {
      ontents->SetPageBaseBackgroundColor(ParseHexColor(color_name));
    } else {