### 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 for an issue that matches the one I want to file, without success.

### Issue Details

* **Electron Version:**
  * 10.1.1
* **Operating System:**
  * macOS 10.15.4

We recently started launching as hidden on macOS (that is, `show: false` or `browserWindow.hide()` while loading the page, followed by `browserWindow.show()` when the dock icon is clicked). This results in some busted focus behavior on the first activation of the window. The second activation restores it.

### Expected Behavior
The guest page receives a `focus` event on the first activation of the app, when created with `show: false`.

### Actual Behavior
The guest page doesn't receive the first `focus` event. Subsequent activations do trigger a `focus` event.

### To Reproduce
[Electron Fiddle](https://gist.github.com/CharlieHess/c507468cd40630d04f58c6514100b997)

shell/browser/api/electron_api_web_contents.cc
mojo::PendingReceiver<mojom::ElectronBrowser> receiver,
    content::RenderFrameHost* render_frame_host) {
  auto id = receivers_.Add(this, std::move(receiver), render_frame_host);
  frame_to_receivers_map_[render_frame_host].push_back(id);
}
void WebContents::OnElectronBrowserConnectionError() {
  auto receiver_id = receivers_.current_receiver();
  auto* frame_host = receivers_.current_context();
  base::Erase(frame_to_receivers_map_[frame_host], receiver_id);
}
void WebContents::Message(bool internal,