message: Tiny refactoring.
diff: class WindowStack
  {
  public:
  - typedef std::list<Window*> WindowList;
  -
  -public:
  -
  WindowStack();
  ~WindowStack();
  @@ -30,7 +26,8 @@ public:
  void update();
  -protected:
  +private:
  + typedef std::list<Window*> WindowList;
  private:
  WindowList mWindowList;
  