old_contents: Player.prototype = Object.create(BasePlayer.prototype);
  Player.prototype.constructor = Player;
  
  /**
   * Player
   *
   * @param {SocketClient} client
   * @param {String} name
   * @param {String} color
   */
  function Player(client, name, color, mail)
  {
      BasePlayer.call(this, client, name, color, mail);
  }
new_contents: /**
   * Player
   *
   * @param {SocketClient} client
   * @param {String} name
   * @param {String} color
   */
  function Player(client, name, color, mail)
  {
      BasePlayer.call(this, client, name, color, mail);
  }
  
  Player.prototype = Object.create(BasePlayer.prototype);
  Player.prototype.constructor = Player;
subject: move prototype after constructor definition