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.cc
SetResizable(resizable);
  }
#endif
#if defined(OS_WIN) || defined(USE_X11)
  bool closable;
  if (options.Get(options::kClosable, &closable)) {
    SetClosable(closable);
  }
#endif
  bool movable;
  if (options.Get(options::kMovable, &movable)) {
    SetMovable(movable);
  }
  bool has_shadow;
  if (options.Get(options::kHasShadow, &has_shadow)) {
    SetHasShadow(has_shadow);
  }
  bool top;
  if (options.Get(options::kAlwaysOnTop, &top) && top) {
    SetAlwaysOnTop(true);
  }
  bool fullscreenable = true;
  bool fullscreen = false;
  if (options.Get(options::kFullscreen, &fullscreen) && !fullscreen) {
    
  #if defined(OS_MACOSX)
    fullscreenable = false;
  #endif
  }