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.cc
#include "atom/browser/api/atom_api_window.h"
#include "atom/common/native_mate_converters/value_converter.h"
#include "atom/browser/api/atom_api_menu.h"
#include "atom/browser/api/atom_api_web_contents.h"
#include "atom/browser/browser.h"
#include "atom/browser/native_window.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/gfx_converter.h"
#include "atom/common/native_mate_converters/gurl_converter.h"
#include "atom/common/native_mate_converters/image_converter.h"
#include "atom/common/native_mate_converters/string16_converter.h"
#include "atom/common/node_includes.h"
#include "atom/common/options_switches.h"
#include "base/command_line.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/common/content_switches.h"