### 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 "mojo/public/cpp/bindings/pending_receiver.h"
#include "mojo/public/cpp/bindings/remote.h"
#include "mojo/public/cpp/system/platform_handle.h"
#include "ppapi/buildflags/buildflags.h"
#include "printing/buildflags/buildflags.h"
#include "printing/print_job_constants.h"
#include "services/service_manager/public/cpp/interface_provider.h"
#include "shell/browser/api/electron_api_browser_window.h"
#include "shell/browser/api/electron_api_debugger.h"
#include "shell/browser/api/electron_api_session.h"
#include "shell/browser/api/electron_api_web_frame_main.h"
#include "shell/browser/api/message_port.h"
#include "shell/browser/browser.h"
#include "shell/browser/child_ontents_tracker.h"
#include "shell/browser/electron_autofill_driver_factory.h"
#include "shell/browser/electron_browser_client.h"
#include "shell/browser/electron_browser_context.h"
#include "shell/browser/electron_browser_main_parts.h"
#include "shell/browser/electron_javascript_dialog_manager.h"
#include "shell/browser/electron_navigation_throttle.h"
#include "shell/browser/native_window.h"
#include "shell/browser/session_preferences.h"
#include "shell/browser/ui/drag_util.h"
#include "shell/browser/ui/file_dialog.h"
#include "shell/browser/ui/inspectable_ontents.h"
#include "shell/browser/ui/inspectable_ontents_view.h"
#include "shell/browser/ontents_permission_helper.h"
#include "shell/browser/ontents_preferences.h"
#include "shell/browser/ontents_zoom_controller.h"
#include "shell/browser/web_dialog_helper.h"