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
parent_window_.Reset(isolate, parent.ToV8());
  
  window_.reset(NativeWindow::Create(
      web_contents->managed_web_contents(),
      options,
      parent.IsEmpty() ? nullptr : parent->window_.get()));
  web_contents->SetOwnerWindow(window_.get());
#if defined(TOOLKIT_VIEWS)
  
  mate::Handle<NativeImage> icon;
  if (options.Get(options::kIcon, &icon))
    SetIcon(icon);
#endif
  window_->InitFromOptions(options);
  window_->AddObserver(this);
  InitWith(isolate, wrapper);
  AttachAsUserData(window_.get());
  
  
  if (!parent.IsEmpty())
    parent->child_windows_.Set(isolate, ID(), wrapper);
}
Window::~Window() {
  if (!window_->IsClosed())
    window_->CloseContents(nullptr);
  
  
  base::MessageLoop::current()->DeleteSoon(FROM_HERE, window_.release());
}
void Window::WillCloseWindow(bool* prevent_default) {