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
WindowList::WindowCloseCancelled(this);
  
  window_unresposive_closure_.Cancel();
}
void NativeWindow::DidFirstVisuallyNonEmptyPaint() {
  if (IsVisible())
    return;
  
  
  const auto view = web_contents()->GetRenderWidgetHostView();
  view->Show();
  view->SetSize(GetContentSize());
  
  base::MessageLoop::current()->PostTask(
      FROM_HERE,
      base::Bind(&NativeWindow::NotifyReadyToShow, GetWeakPtr()));
}
bool NativeWindow::OnMessageReceived(const IPC::Message& message) {
  bool handled = true;
  IPC_BEGIN_MESSAGE_MAP(NativeWindow, message)
    IPC_MESSAGE_HANDLER(AtomViewHostMsg_UpdateDraggableRegions,
                        UpdateDraggableRegions)
    IPC_MESSAGE_UNHANDLED(handled = false)
  IPC_END_MESSAGE_MAP()
  return handled;
}
void NativeWindow::UpdateDraggableRegions(