This virtual method mimics the behaviour of mutation observers and make it more viable than the older child_inserted(), which didn't cover removed nodes and was called as many times as there were inserted nodes. A few other shortcomings where remove_child() was called directly instead of Node::remove() were also fixed while at it. Source-Repo: https://github.com/servo/servo Source-Revision: 705c95dedbbaa60ffd08e70579915e228d5b6ee0