### 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
static_cast<ElectronBrowserClient*>(ElectronBrowserClient::Get())
      ->set_delegate(this);
  Browser::Get()->AddObserver(this);
  auto pid = content::ChildProcessHost::kInvalidUniqueID;
  auto process_metric = std::make_unique<electron::ProcessMetric>(
      content::PROCESS_TYPE_BROWSER, base::GetCurrentProcessHandle(),
      base::ProcessMetrics::CreateCurrentProcessMetrics());
  app_metrics_[pid] = std::move(process_metric);
}
App::~App() {
  static_cast<ElectronBrowserClient*>(ElectronBrowserClient::Get())
      ->set_delegate(nullptr);
  Browser::Get()->RemoveObserver(this);
  content::GpuDataManager::GetInstance()->RemoveObserver(this);
  content::BrowserChildProcessObserver::Remove(this);
}
void App::OnBeforeQuit(bool* prevent_default) {
  if (Emit("before-quit")) {
    *prevent_default = true;
  }
}
void App::OnWillQuit(bool* prevent_default) {