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
*prevent_default = Emit("close");
}
void Window::WillDestoryNativeObject() {
  
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  for (v8::Local<v8::Value> value : child_windows_.Values(isolate())) {
    mate::Handle<Window> child;
    if (mate::ConvertFromV8(isolate(), value, &child))
      child->window_->CloseImmediately();
  }
}
void Window::OnWindowClosed() {
  api_web_contents_->DestroyWebContents();
  RemoveFromWeakMap();
  window_->RemoveObserver(this);
  
  
  MarkDestroyed();
  Emit("closed");
  RemoveFromParentChildWindows();
  
  base::MessageLoop::current()->PostTask(FROM_HERE, GetDestroyClosure());
}
void Window::OnWindowBlur() {