### 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
#if !defined(OS_WIN)
  static constexpr base::TaskTraits kTraits = {
      base::MayBlock(), base::TaskPriority::USER_VISIBLE};
#endif
#if defined(USE_CUPS)
  
  return base::ThreadPool::CreateTaskRunner(kTraits);
#elif defined(OS_WIN)
  
  
  return content::GetUIThreadTaskRunner(
      {base::MayBlock(), base::TaskPriority::USER_VISIBLE});
#else
  
  return base::ThreadPool::CreateSingleThreadTaskRunner(kTraits);
#endif
}
#endif
struct UserDataLink : public base::SupportsUserData::Data {
  explicit UserDataLink(base::WeakPtr<WebContents> contents)