### 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.

### Problem Description

We need to load a custom error page when the certificate is invalid but without "isMainFrame" property we don't know when to load the custom error page using webContents.loadURL()

### Proposed Solution

webContents.on("certificate-error", ((event, url, error, certificate, callback, isMainFrame)

### Alternatives Considered

Not sure

### Additional Information

Not sure
shell/browser/api/electron_api_app.cc
#if defined(OS_LINUX)
  auto env = base::Environment::Create();
  env->SetVar("CHROME_DESKTOP", desktop_name);
#endif
}
std::string App::GetLocale() {
  return g_browser_process->GetApplicationLocale();
}
std::string App::GetLocaleCountryCode() {
  std::string region;
#if defined(OS_WIN)
  WCHAR locale_name[LOCALE_NAME_MAX_LENGTH] = {0};
  if (GetLocaleInfoEx(LOCALE_NAME_USER_DEFAULT, LOCALE_SISO3166CTRYNAME,
                      (LPWSTR)&locale_name,
                      sizeof(locale_name) / sizeof(WCHAR)) ||
      GetLocaleInfoEx(LOCALE_NAME_SYSTEM_DEFAULT, LOCALE_SISO3166CTRYNAME,
                      (LPWSTR)&locale_name,
                      sizeof(locale_name) / sizeof(WCHAR))) {
    base::WideToUTF8(locale_name, wcslen(locale_name), &region);
  }
#elif defined(OS_MAC)
  CFLocaleRef locale = CFLocaleCopyCurrent();
  CFStringRef value = CFStringRef(
      static_cast<CFTypeRef>(CFLocaleGetValue(locale, kCFLocaleCountryCode)));
  const CFIndex kCStringSize = 128;