code: function(){
  		if(this.position<this.initpos){ this.broken = true;}
  		for(var i=this.history.length-1;i>=this.position;i--){ this.history.pop();}
  		this.position = this.history.length;
  		this.chainflag = false;
  	}
docs: --------------------------------------------------------------------------- opemgr.removeDescendant()  現在以降の履歴を消去する ---------------------------------------------------------------------------