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 (is_modal() && NativeWindow::parent()) {
    NativeWindowViews* parent =
        static_cast<NativeWindowViews*>(NativeWindow::parent());
    
    parent->SetEnabled(true);
    
    parent->Focus(true);
  }
  NotifyWindowClosed();
}
views::View* NativeWindowViews::GetInitiallyFocusedView() {
  return inspectable_web_contents()->GetView()->GetWebView();
}
bool NativeWindowViews::CanResize() const {
  return resizable_;
}
bool NativeWindowViews::CanMaximize() const {
  return resizable_ && maximizable_;
}
bool NativeWindowViews::CanMinimize() const {
#if defined(OS_WIN)
  return minimizable_;
#elif defined(USE_X11)
  return true;
#endif
}
base::string16 NativeWindowViews::GetWindowTitle() const {