### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/main/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/main/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 bug report that matches the one I want to file, without success.

### Electron Version

16.0.0

### What operating system are you using?

Windows

### Operating System Version

WIN10 20H2

### What arch are you using?

x64

### Last Known Working Electron version

_No response_

### Expected Behavior

 win.webContents.savePage('d:/aaaaaa.html', 'HTMLComplete').then(() => {
      console.log('Page was saved successfully.')
    }).catch(err => {
      console.log(err)
    })

it will generate a html page file at d: 

### Actual Behavior

savePage has three formats that can be used

if use HTMLComplete
 only produced a aaaaaa_files empty folder

if use HTMLonly 
No files are generated nor error callbacks are generated

MHTML option works fine

### Testcase Gist URL

_No response_

### Additional Information

_No response_
shell/browser/api/electron_api_web_contents.cc
const content::WebContents* source) {
  return html_fullscreen_;
}
bool WebContents::TakeFocus(content::WebContents* source, bool reverse) {
  if (source && source->GetOutermostWebContents() == source) {
     If this is the outermost web contents and the user has tabbed or
     shift + tabbed through all the elements, reset the focus back to
     the first or last element so that it doesn't stay in the body.
    source->FocusThroughTabTraversal(reverse);
    return true;
  }
  return false;
}
content::PictureInPictureResult WebContents::EnterPictureInPicture(
    content::WebContents* ontents,
    const viz::SurfaceId& surface_id,
    const gfx::Size& natural_size) {
#if BUILDFLAG(ENABLE_PICTURE_IN_PICTURE)
  return PictureInPictureWindowManager::GetInstance()->EnterPictureInPicture(
      ontents, surface_id, natural_size);
#else
  return content::PictureInPictureResult::kNotSupported;
#endif
}
void WebContents::ExitPictureInPicture() {
#if BUILDFLAG(ENABLE_PICTURE_IN_PICTURE)
  PictureInPictureWindowManager::GetInstance()->ExitPictureInPicture();
#endif
}
void WebContents::DevToolsSaveToFile(const std::string& url,