### 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
bool initially_shown = type_ != Type::BROWSER_VIEW;
  options.Get(options::kShow, &initially_shown);
  
  std::string partition;
  gin::Handle<api::Session> session;
  if (options.Get("session", &session) && !session.IsEmpty()) {
  } else if (options.Get("partition", &partition)) {
    session = Session::FromPartition(isolate, partition);
  } else {
    
    session = Session::FromPartition(isolate, "");
  }
  session_.Reset(isolate, session.ToV8());
  std::unique_ptr<content::WebContents> ontents;
  if (IsGuest()) {
    scoped_refptr<content::SiteInstance> site_instance =
        content::SiteInstance::CreateForURL(session->browser_context(),
                                            GURL("chrome-guest:fake-host"));
    content::WebContents::CreateParams params(session->browser_context(),
                                              site_instance);
    guest_delegate_ =
        std::make_unique<WebViewGuestDelegate>(embedder_->ontents(), this);
    params.guest_delegate = guest_delegate_.get();
#if BUILDFLAG(ENABLE_OSR)
    if (embedder_ && embedder_->IsOffScreen()) {
      auto* view = new OffScreenWebContentsView(
          false,