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_views.h
views::NonClientFrameView* CreateNonClientFrameView(
      views::Widget* widget) override;
  void OnWidgetMove() override;
#if defined(OS_WIN)
  bool ExecuteWindowsCommand(int command_id) override;
#endif
#if defined(OS_WIN)
  
  bool PreHandleMSG(
      UINT message, WPARAM w_param, LPARAM l_param, LRESULT* result) override;
  void HandleSizeEvent(WPARAM w_param, LPARAM l_param);
#endif
  
  gfx::Size ContentSizeToWindowSize(const gfx::Size& size) override;
  gfx::Size WindowSizeToContentSize(const gfx::Size& size) override;
  void HandleKeyboardEvent(
      content::WebContents*,
      const content::NativeWebKeyboardEvent& event) override;
  
  gfx::Size GetMinimumSize() override;
  gfx::Size GetMaximumSize() override;
  bool AcceleratorPressed(const ui::Accelerator& accelerator) override;
  
  void RegisterAccelerators(AtomMenuModel* menu_model);
  
  ui::WindowShowState GetRestoredState();
  std::unique_ptr<views::Widget> window_;
  views::View* web_view_;  
  std::unique_ptr<MenuBar> menu_bar_;
  bool menu_bar_autohide_;