TitleBarRect
dirty.Include(otherDecorator->TitleBarRect());
dirty.Include(decorator->TitleBarRect());
tabFrame = decorator->TitleBarRect();
BRect TitleBarRect() const;
BRect tabRect = decorator->TitleBarRect();
if (!window->Decorator()->TitleBarRect().Contains(mousePosition))
mousePosition.y = window->Decorator()->TitleBarRect().top;