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
menu_bar_->ActivateAccelerator(event.windowsKeyCode);
    return;
  }
  if (!menu_bar_autohide_)
    return;
  
  if (event.type == blink::WebInputEvent::RawKeyDown && IsAltKey(event)) {
    
    menu_bar_alt_pressed_ = true;
  } else if (event.type == blink::WebInputEvent::KeyUp && IsAltKey(event) &&
             menu_bar_alt_pressed_) {
    
    menu_bar_alt_pressed_ = false;
    SetMenuBarVisibility(!menu_bar_visible_);
  } else {
    
    menu_bar_alt_pressed_ = false;
  }
}
gfx::Size NativeWindowViews::GetMinimumSize() {
  return NativeWindow::GetMinimumSize();
}
gfx::Size NativeWindowViews::GetMaximumSize() {
  return NativeWindow::GetMaximumSize();
}
bool NativeWindowViews::AcceleratorPressed(const ui::Accelerator& accelerator) {
  return accelerator_util::TriggerAcceleratorTableCommand(
      &accelerator_table_, accelerator);
}
void NativeWindowViews::RegisterAccelerators(AtomMenuModel* menu_model) {