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
NativeWindow::SetParentWindow(parent);
#if defined(USE_X11)
  XDisplay* xdisplay = gfx::GetXDisplay();
  XSetTransientForHint(
      xdisplay, GetAcceleratedWidget(),
      parent? parent->GetAcceleratedWidget() : DefaultRootWindow(xdisplay));
#elif defined(OS_WIN) && defined(DEBUG)
  
  
  if (parent) {
    ::SetParent(GetAcceleratedWidget(), parent->GetAcceleratedWidget());
    views::Widget::ReparentNativeView(GetNativeWindow(),
                                      parent->GetNativeWindow());
    wm::AddTransientChild(parent->GetNativeWindow(), GetNativeWindow());
  } else {
    if (!GetNativeWindow()->parent())
      return;
    ::SetParent(GetAcceleratedWidget(), NULL);
    views::Widget::ReparentNativeView(GetNativeWindow(), nullptr);
    wm::RemoveTransientChild(GetNativeWindow()->parent(), GetNativeWindow());
  }
#endif
}
gfx::NativeWindow NativeWindowViews::GetNativeWindow() {