### 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.h
content::SiteInstance* source_site_instance,
      bool is_new_browsing_instance,
      const GURL& opener_url,
      const std::string& frame_name,
      const GURL& target_url,
      const std::string& partition_id,
      content::SessionStorageNamespace* session_storage_namespace) override;
  void WebContentsCreatedWithFullParams(
      content::WebContents* source_contents,
      int opener_render_process_id,
      int opener_render_frame_id,
      const content::mojom::CreateNewWindowParams& params,
      content::WebContents* new_contents) override;
  void AddNewContents(content::WebContents* source,
                      std::unique_ptr<content::WebContents> new_contents,
                      const GURL& target_url,
                      WindowOpenDisposition disposition,
                      const gfx::Rect& initial_rect,
                      bool user_gesture,
                      bool* was_blocked) override;
  content::WebContents* OpenURLFromTab(
      content::WebContents* source,
      const content::OpenURLParams& params) override;
  void BeforeUnloadFired(content::WebContents* tab,
                         bool proceed,
                         bool* proceed_to_fire_unload) override;
  void SetContentsBounds(content::WebContents* source,
                         const gfx::Rect& pos) override;
  void CloseContents(content::WebContents* source) override;
  void ActivateContents(content::WebContents* contents) override;