### 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
blink::WebMouseWheelEvent mouse_wheel_event;
    if (gin::ConvertFromV8(isolate, input_event, &mouse_wheel_event)) {
      if (IsOffScreen()) {
#if BUILDFLAG(ENABLE_OSR)
        GetOffScreenRenderWidgetHostView()->SendMouseWheelEvent(
            mouse_wheel_event);
#endif
      } else {
         Chromium expects phase info in wheel events (and applies a
         DCHECK to verify it). See: https:crbug.com/756524.
        mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseBegan;
        mouse_wheel_event.dispatch_type =
            blink::WebInputEvent::DispatchType::kBlocking;
        rwh->ForwardWheelEvent(mouse_wheel_event);
         Send a synthetic wheel event with phaseEnded to finish scrolling.
        mouse_wheel_event.has_synthetic_phase = true;
        mouse_wheel_event.delta_x = 0;
        mouse_wheel_event.delta_y = 0;
        mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseEnded;
        mouse_wheel_event.dispatch_type =
            blink::WebInputEvent::DispatchType::kEventNonBlocking;
        rwh->ForwardWheelEvent(mouse_wheel_event);
      }
      return;
    }
  }
  isolate->ThrowException(
      v8::Exception::Error(gin::StringToV8(isolate, "Invalid event object")));
}
void WebContents::BeginFrameSubscription(gin::Arguments* args) {