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.h
content::WebContents*,
      const content::NativeWebKeyboardEvent& event) {}
  
  
  void NotifyWindowClosed();
  void NotifyWindowBlur();
  void NotifyWindowFocus();
  void NotifyWindowShow();
  void NotifyWindowHide();
  void NotifyWindowMaximize();
  void NotifyWindowUnmaximize();
  void NotifyWindowMinimize();
  void NotifyWindowRestore();
  void NotifyWindowMove();
  void NotifyWindowResize();
  void NotifyWindowMoved();
  void NotifyWindowScrollTouchBegin();
  void NotifyWindowScrollTouchEnd();
  void NotifyWindowSwipe(const std::string& direction);
  void NotifyWindowEnterFullScreen();
  void NotifyWindowLeaveFullScreen();
  void NotifyWindowEnterHtmlFullScreen();
  void NotifyWindowLeaveHtmlFullScreen();
  void NotifyWindowExecuteWindowsCommand(const std::string& command);
  #if defined(OS_WIN)
  void NotifyWindowMessage(UINT message, WPARAM w_param, LPARAM l_param);
  #endif
  void AddObserver(NativeWindowObserver* obs) {