* **Electron Version:**
  4.0.2
* **Operating System:**
  macOS 10.14.3
* **Last Known Working Electron version:**:
  1.7

### Expected Behavior
When creating a BrowserWindow it should not appear in the dock menu by defaults.

### Actual Behavior
It appears in the dock menu (example: `raven` in https://electronjs.org/docs/tutorial/macos-dock)

### To Reproduce
Just create new BrowserWindow, then right click on the app icon in the dock. (see https://electronjs.org/docs/tutorial/macos-dock)

At least it should be a way to control that, this can be achieve for top level window with:
`[window_ setExcludedFromWindowsMenu:YES];`, indeed [window isExcludedFromWindowsMenu] returns false by default, see

https://developer.apple.com/documentation/appkit/nsapplication/1428625-removewindowsitem
`Use the isExcludedFromWindowsMenu method of NSWindow if you want the item to remain excluded from the Window menu.`
https://developer.apple.com/documentation/appkit/nswindow/1419175-isexcludedfromwindowsmenu

atom/browser/native_window_mac.h
AtomPreviewItem* preview_item() const { return preview_item_.get(); }
  AtomTouchBar* touch_bar() const { return touch_bar_.get(); }
  bool zoom_to_page_width() const { return zoom_to_page_width_; }
  bool fullscreen_window_title() const { return fullscreen_window_title_; }
  bool simple_fullscreen() const { return always_simple_fullscreen_; }
 protected:
  
  bool CanResize() const override;
  views::View* GetContentsView() override;
 private:
  
  void AddContentViewLayers();
  void InternalSetParentWindow(NativeWindow* parent, bool attach);
  void SetForwardMouseMessages(bool forward);
  AtomNSWindow* window_;  
  base::scoped_nsobject<AtomNSWindowDelegate> window_delegate_;
  base::scoped_nsobject<AtomPreviewItem> preview_item_;
  base::scoped_nsobject<AtomTouchBar> touch_bar_;
  base::scoped_nsobject<CustomWindowButtonView> buttons_view_;
  
  id wheel_event_monitor_;
  
  base::scoped_nsobject<FullSizeContentView> container_view_;
  
  std::unique_ptr<RootViewMac> root_view_;