**Do you want to request a *feature* or report a *bug*?**
bug

**What is the current behavior?**
React 15.x was able to render within a DocumentFragment/shadowRoot, not possible with Fiber anymore

**DEMO**

https://www.webpackbin.com/bins/-KvPFG7-HGfQ34IgUxQt

```js
import React, {Component} from 'react'
import {render} from 'react-dom'


class MyComponent extends Component{
  render(){
    return <div>Hello From React !</div>
  }
}

class MyElement extends HTMLElement {
  static is = 'my-element'
  constructor(){
    super()
    const shadowRoot = this.attachShadow({mode:'open'})
    try {
      // this fails 
      render(<MyComponent/>, shadowRoot)
    } catch (e){
      console.error(e)
      shadowRoot.innerHTML = `
        <div style="color:red;">${e}</div>
        <div>see console log for stack trace</div>
       `
    }
  }
  connectedCallback(){
    console.log('MyElement mounted!')
  }
}

customElements.define(MyElement.is, MyElement)
```


related -> https://github.com/skatejs/renderer-react/issues/3

**What is the expected behavior?**
be able to render to shadow root like previous versions of React

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
React 16
Chrome

wrapperConstructor.prototype[name] = function() {
        return wrapNodeList(unsafeUnwrap(this)[name].apply(unsafeUnwrap(this), arguments));
      };
    }
    scope.wrappers.NodeList = NodeList;
    scope.addWrapNodeListMethod = addWrapNodeListMethod;
    scope.wrapNodeList = wrapNodeList;
  })(window.ShadowDOMPolyfill);
  (function(scope) {
    "use strict";
    scope.wrapHTMLCollection = scope.wrapNodeList;
    scope.wrappers.HTMLCollection = scope.wrappers.NodeList;
  })(window.ShadowDOMPolyfill);
  (function(scope) {
    "use strict";
    var EventTarget = scope.wrappers.EventTarget;
    var NodeList = scope.wrappers.NodeList;
    var TreeScope = scope.TreeScope;
    var assert = scope.assert;
    var defineWrapGetter = scope.defineWrapGetter;
    var enqueueMutation = scope.enqueueMutation;
    var getTreeScope = scope.getTreeScope;
    var isWrapper = scope.isWrapper;
    var mixin = scope.mixin;
    var registerTransientObservers = scope.registerTransientObservers;
    var registerWrapper = scope.registerWrapper;