版本（versions）：
react@16.0.0
react-dom@16.0.0

描述（description）：
给父级别绑定 onMouseEnter 事件。在首次渲染后，鼠标移入新渲染进去的子元素会触发父元素的 onMouseEnter 事件。

示例（demo）：

```js
import React, {Component} from 'react';

class Demo extends Component {
    constructor(prop) {
        super(prop);
        this.enter = this.enter.bind(this)
        this.state = {
            flag: false
        }
    }
    enter(event) {
        console.log(event.nativeEvent);
        console.log("enter")
    }
    click() {
        this.setState({flag:!this.state.flag})
    }
    render() {
        let old = {
            height: "100px",
            width: "100px",
            border: "1px solid #6dbbff"
        };
        let aa = {
            height: "100px",
            width: "100px",
            border: "1px solid red"
        };
        let content = {
            border: "1px solid black",
            display: "flex",
            padding:"10px"
        }
        return(
            <div>
                <div style={content} onMouseEnter={this.enter}>
                    {this.state.a}
                    <div style={old}>old</div>
                    <div style={aa}>old</div>
                    {this.state.flag && <div style={aa}>new</div>}
                </div>
                <button onClick={this.click.bind(this)}>点我（click me）</button>
            </div>
        )
    }
}
```
/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @providesModule ReactTreeTraversal
 */
'use strict';
var {HostComponent} = require('ReactTypeOfWork');
function getParent(inst) {
  do {
    inst = inst.return;
    
    
    
    
    
  } while (inst && inst.tag !== HostComponent);
  if (inst) {
    return inst;
  }
  return null;
}
/**
 * Return the lowest common ancestor of A and B, or null if they are in
 * different trees.
 */
function getLowestCommonAncestor(instA, instB) {