I use `ReactDOM.unstable_renderSubtreeIntoContainer` to render a portal.

``` javascript
class Modal extends React.Component {

componentDidMount() {
    this.node = document.createElement('div');
    document.body.appendChild(this.node);
    this.renderPortal(this.props);
}

componentWillReceiveProps(nextProps) {
    this.renderPortal(nextProps);
}

componentWillUnmount() {
    ReactDOM.unmountComponentAtNode(this.node);
    document.body.removeChild(this.node);
}

renderPortal = (props) => {
    renderSubtreeIntoContainer(this, <ModalPortal {...props} />, this.node);
}

render() {
    return null;
  }
}
```

In my root component:

``` javascript
class App extends React.Component {
    static childContextTypes = {
        highlightColor: React.PropTypes.object
    }

    getChildContext() {
        return {
            highlightColor: this.props.highlightColor
        }
    }

    ...
}
```

The context of root component will be updated and passed to children if  `this.props.highlightColor` is changed. This is right.
I can access the correct context in the `<ModalPortal/>` component in the first render.
And after that the context passed to  `<ModalPortal/>` **does not change any more** when the context of root component changed.
But I can access the correct context in the `<Modal/>`  every render.

what's wrong with my code ?

TopLevelWrapper: TopLevelWrapper,
  /**
   * Used by devtools. The keys are not important.
   */
  _instancesByReactRootID: instancesByReactRootID,
  /**
   * This is a hook provided to support rendering React components while
   * ensuring that the apparent scroll position of its `container` does not
   * change.
   *
   * @param {DOMElement} container The `container` being rendered into.
   * @param {function} renderCallback This must be called once to do the render.
   */
  scrollMonitor: function(container, renderCallback) {
    renderCallback();
  },
  /**
   * Take a component that's already mounted into the DOM and replace its props
   * @param {ReactComponent} prevComponent component instance already in the DOM
   * @param {ReactElement} nextElement component instance to render
   * @param {DOMElement} container container to render into
   * @param {?function} callback function triggered on completion
   */
  _updateRootComponent: function(
      prevComponent,
      nextElement,
      container,
      callback) {
    ReactMount.scrollMonitor(container, function() {
      ReactUpdateQueue.enqueueElementInternal(prevComponent, nextElement);