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/api/atom_api_window.h
protected:
  Window(v8::Isolate* isolate, v8::Local<v8::Object> wrapper,
         const mate::Dictionary& options);
  ~Window() override;
  
  void WillCloseWindow(bool* prevent_default) override;
  void WillDestoryNativeObject() override;
  void OnWindowClosed() override;
  void OnWindowBlur() override;
  void OnWindowFocus() override;
  void OnWindowShow() override;
  void OnWindowHide() override;
  void OnReadyToShow() override;
  void OnWindowMaximize() override;
  void OnWindowUnmaximize() override;
  void OnWindowMinimize() override;
  void OnWindowRestore() override;
  void OnWindowResize() override;
  void OnWindowMove() override;
  void OnWindowMoved() override;
  void OnWindowScrollTouchBegin() override;
  void OnWindowScrollTouchEnd() override;
  void OnWindowSwipe(const std::string& direction) override;
  void OnWindowEnterFullScreen() override;
  void OnWindowLeaveFullScreen() override;
  void OnWindowEnterHtmlFullScreen() override;
  void OnWindowLeaveHtmlFullScreen() override;
  void OnRendererUnresponsive() override;
  void OnRendererResponsive() override;
  void OnExecuteWindowsCommand(const std::string& command_name) override;