We can get the content size and the window size, but not the chrome position.

At the moment we do this:

```
leftBorderWidth = (windowWidth - contentWidth) / 2;
titlebarHeight = windowHeight - (contentHeight + leftBorderWidth);
```

which makes some assumptions so therefore feels a bit wrong.

it would be nice if alongside getContentSize (https://github.com/electron/electron/blob/master/docs/api/browser-window.md#wingetcontentsize) there was a getContentOffset.

I've been looking at the C++ - https://github.com/electron/electron/blob/e05804848f98959d63337aacd9047cd579c5b23f/chromium_src/extensions/browser/app_window/size_constraints.cc and I don't see an easy way to get this information - do you have any ideas or pointers if you accept this as a feature request?

atom/browser/native_window_mac.h
const std::vector<DraggableRegion>& regions, int width, int height);
 private:
  
  gfx::Size ContentSizeToWindowSize(const gfx::Size& size) override;
  gfx::Size WindowSizeToContentSize(const gfx::Size& size) override;
  void UpdateDraggableRegions(
      const std::vector<DraggableRegion>& regions) override;
  void InstallView();
  void UninstallView();
  
  
  void UpdateDraggableRegionViews(const std::vector<DraggableRegion>& regions);
  base::scoped_nsobject<AtomNSWindow> window_;
  base::scoped_nsobject<AtomNSWindowDelegate> window_delegate_;
  
  id wheel_event_monitor_;
  
  base::scoped_nsobject<FullSizeContentView> content_view_;
  std::vector<DraggableRegion> draggable_regions_;
  bool is_kiosk_;
  NSInteger attention_request_id_;  
  
  NSApplicationPresentationOptions kiosk_options_;
  
  TitleBarStyle title_bar_style_;
  DISALLOW_COPY_AND_ASSIGN(NativeWindowMac);
};
}  
#endif