
### 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:**
  * 6.1.5
* **Operating System:**
  * Windows 10
* **Last Known Working Electron version:**
  * ?

### Expected Behavior
If the window is focusable then the focus event should be triggered

### Actual Behavior
Setting the window initially to focusable: false and later to true again will not enable the focus events. Even when focusing the window, the event will never be triggered.

### To Reproduce
```
let browserWindow1 = new BrowserWindow({
	show: false,
	x: 1,
	y: 1,
	width: 800,
	height: 700,
	title: "test-title-1",
	focusable: false,
});
browserWindow1.on("focus", () => {console.log("focus");});
browserWindow1.loadURL("http://www.google.com");
browserWindow1.setFocusable(true);
browserWindow1.show();
```

shell/browser/native_window_views.cc
display::Screen::GetScreen()->GetDisplayNearestPoint(GetPosition());
      SetBounds(display.bounds(), false);
    } else {
      SetBounds(restore_bounds_, false);
    }
    return;
  }
  
  
  widget()->SetFullscreen(fullscreen);
  
  
  
  
  if (leaving_fullscreen && !IsVisible())
    FlipWindowStyle(GetAcceleratedWidget(), true, WS_VISIBLE);
#else
  if (IsVisible())
    widget()->SetFullscreen(fullscreen);
  else if (fullscreen)
    widget()->native_widget_private()->Show(ui::SHOW_STATE_FULLSCREEN,
                                            gfx::Rect());
  
  if (fullscreen)
    SetMenuBarVisibility(false);
  else
    SetMenuBarVisibility(!IsMenuBarAutoHide());
#endif
}
bool NativeWindowViews::IsFullscreen() const {