在mouseMove addChild 在mouseDown removeChild，这里操作的不是同一个Node，如果同时移动和按下鼠标就会有一定几率导致崩溃，CCASSERT(!_running, “Node still marked as running on node destruction! Was base class onExit() called in derived class onExit() implementations?”);
疯了才会再move里addChild，这里快的话每一帧都会调起