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_views.cc
#if defined(OS_WIN)
  base::win::ScopedComPtr<ITaskbarList> taskbar;
  if (FAILED(taskbar.CreateInstance(CLSID_TaskbarList, NULL,
                                    CLSCTX_INPROC_SERVER)) ||
      FAILED(taskbar->HrInit()))
    return;
  if (skip)
    taskbar->DeleteTab(GetAcceleratedWidget());
  else
    taskbar->AddTab(GetAcceleratedWidget());
#elif defined(USE_X11)
  SetWMSpecState(GetAcceleratedWidget(), skip,
                 GetAtom("_NET_WM_STATE_SKIP_TASKBAR"));
#endif
}
void NativeWindowViews::SetKiosk(bool kiosk) {