### 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
base::ProcessId plugin_pid) {
#if BUILDFLAG(ENABLE_PLUGINS)
  content::WebPluginInfo info;
  auto* plugin_service = content::PluginService::GetInstance();
  plugin_service->GetPluginInfoByPath(plugin_path, &info);
  Emit("plugin-crashed", info.name, info.version);
#endif  
}
void WebContents::MediaStartedPlaying(const MediaPlayerInfo& video_type,
                                      const content::MediaPlayerId& id) {
  Emit("media-started-playing");
}
void WebContents::MediaStoppedPlaying(
    const MediaPlayerInfo& video_type,
    const content::MediaPlayerId& id,
    content::WebContentsObserver::MediaStoppedReason reason) {
  Emit("media-paused");
}
void WebContents::DidChangeThemeColor() {
  auto theme_color = ontents()->GetThemeColor();
  if (theme_color) {
    Emit("did-change-theme-color", electron::ToRGBHex(theme_color.value()));
  } else {
    Emit("did-change-theme-color", nullptr);
  }
}
void WebContents::OnInterfaceRequestFromFrame(