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 (!thick_frame_)
    ex_style |= WS_EX_COMPOSITED;
  if (window_type == "toolbar")
    ex_style |= WS_EX_TOOLWINDOW;
  ::SetWindowLong(GetAcceleratedWidget(), GWL_EXSTYLE, ex_style);
#endif
  
  
  if (has_frame()) {
    window_->set_frame_type(views::Widget::FrameType::FRAME_TYPE_FORCE_NATIVE);
    window_->FrameTypeChanged();
  }
  gfx::Size size = bounds.size();
  if (has_frame() &&
      options.Get(options::kUseContentSize, &use_content_size_) &&
      use_content_size_)
    size = ContentSizeToWindowSize(size);
  window_->CenterWindow(size);
  Layout();
#if defined(OS_WIN)
  
  if (fullscreen)
    last_window_state_ = ui::SHOW_STATE_FULLSCREEN;
  else
    last_window_state_ = ui::SHOW_STATE_NORMAL;
  last_normal_bounds_ = GetBounds();
#endif
}
NativeWindowViews::~NativeWindowViews() {