### 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
.SetMethod("isPainting", &WebContents::IsPainting)
      .SetMethod("setFrameRate", &WebContents::SetFrameRate)
      .SetMethod("getFrameRate", &WebContents::GetFrameRate)
#endif
      .SetMethod("invalidate", &WebContents::Invalidate)
      .SetMethod("setZoomLevel", &WebContents::SetZoomLevel)
      .SetMethod("getZoomLevel", &WebContents::GetZoomLevel)
      .SetMethod("setZoomFactor", &WebContents::SetZoomFactor)
      .SetMethod("getZoomFactor", &WebContents::GetZoomFactor)
      .SetMethod("getType", &WebContents::GetType)
      .SetMethod("_getPreloadPaths", &WebContents::GetPreloadPaths)
      .SetMethod("getWebPreferences", &WebContents::GetWebPreferences)
      .SetMethod("getLastWebPreferences", &WebContents::GetLastWebPreferences)
      .SetMethod("getOwnerBrowserWindow", &WebContents::GetOwnerBrowserWindow)
      .SetMethod("inspectServiceWorker", &WebContents::InspectServiceWorker)
      .SetMethod("inspectSharedWorker", &WebContents::InspectSharedWorker)
      .SetMethod("inspectSharedWorkerById",
                 &WebContents::InspectSharedWorkerById)
      .SetMethod("getAllSharedWorkers", &WebContents::GetAllSharedWorkers)
#if BUILDFLAG(ENABLE_PRINTING)
      .SetMethod("_print", &WebContents::Print)
      .SetMethod("_printToPDF", &WebContents::PrintToPDF)
#endif
      .SetMethod("_setNextChildWebPreferences",
                 &WebContents::SetNextChildWebPreferences)
      .SetMethod("addWorkSpace", &WebContents::AddWorkSpace)
      .SetMethod("removeWorkSpace", &WebContents::RemoveWorkSpace)
      .SetMethod("showDefinitionForSelection",
                 &WebContents::ShowDefinitionForSelection)
      .SetMethod("copyImageAt", &WebContents::CopyImageAt)