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
#ifndef ATOM_BROWSER_API_ATOM_API_WINDOW_H_
#define ATOM_BROWSER_API_ATOM_API_WINDOW_H_
#include <map>
#include <memory>
#include <string>
#include <vector>
#include "ui/gfx/image/image.h"
#include "atom/browser/api/trackable_object.h"
#include "atom/browser/native_window.h"
#include "atom/browser/native_window_observer.h"
#include "atom/common/api/atom_api_native_image.h"
#include "atom/common/key_weak_map.h"
#include "native_mate/handle.h"
class GURL;