### 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
#include "third_party/blink/public/mojom/frame/find_in_page.mojom.h"
#include "third_party/blink/public/mojom/frame/fullscreen.mojom.h"
#include "third_party/blink/public/mojom/messaging/transferable_message.mojom.h"
#include "third_party/blink/public/mojom/renderer_preferences.mojom.h"
#include "ui/base/cursor/cursor.h"
#include "ui/base/cursor/mojom/cursor_type.mojom-shared.h"
#include "ui/display/screen.h"
#include "ui/events/base_event_utils.h"
#if BUILDFLAG(ENABLE_OSR)
#include "shell/browser/osr/osr_render_widget_host_view.h"
#include "shell/browser/osr/osr_ontents_view.h"
#endif
#if !defined(OS_MAC)
#include "ui/aura/window.h"
#else
#include "ui/base/cocoa/defaults_utils.h"
#endif
#if defined(OS_LINUX)
#include "ui/views/linux_ui/linux_ui.h"
#endif
#if defined(OS_LINUX) || defined(OS_WIN)
#include "ui/gfx/font_render_params.h"
#endif
#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
#include "extensions/browser/script_executor.h"
#include "extensions/browser/view_type_utils.h"
#include "extensions/common/mojom/view_type.mojom.h"
#include "shell/browser/extensions/electron_extension_ontents_observer.h"
#endif
#if BUILDFLAG(ENABLE_PRINTING)