### 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
std::string* class_name) {
  *class_name = Browser::Get()->GetName();
  *name = base::ToLowerASCII(*class_name);
}
#endif
void WebContents::OnDevToolsIndexingWorkCalculated(
    int request_id,
    const std::string& file_system_path,
    int total_work) {
  base::Value request_id_value(request_id);
  base::Value file_system_path_value(file_system_path);
  base::Value total_work_value(total_work);
  inspectable_ontents_->CallClientFunction(
      "DevToolsAPI.indexingTotalWorkCalculated", &request_id_value,
      &file_system_path_value, &total_work_value);
}
void WebContents::OnDevToolsIndexingWorked(int request_id,
                                           const std::string& file_system_path,
                                           int worked) {
  base::Value request_id_value(request_id);
  base::Value file_system_path_value(file_system_path);
  base::Value worked_value(worked);
  inspectable_ontents_->CallClientFunction(
      "DevToolsAPI.indexingWorked", &request_id_value, &file_system_path_value,
      &worked_value);
}
void WebContents::OnDevToolsIndexingDone(int request_id,