Hello,

After updating to React 15.0.1, we are getting the following error:

```
Uncaught TypeError: Cannot read property 'addEventListener' of null
```

![image](https://cloud.githubusercontent.com/assets/4996164/14602577/5bb4e9f2-0571-11e6-9aa1-98de49f50d76.png)

'Inner-didUpdate-2-2',
          'Inner-callback-2',
      'Outer-callback-2',
    ]);
    
  });
  it('should flush updates in the correct order across roots', function() {
    var instances = [];
    var updates = [];
    var MockComponent = React.createClass({
      render: function() {
        updates.push(this.props.depth);
        return <div />;
      },
      componentDidMount: function() {
        instances.push(this);
        if (this.props.depth < this.props.count) {
          ReactDOM.render(
            <MockComponent
              depth={this.props.depth + 1}
              count={this.props.count}
            />,
            ReactDOM.findDOMNode(this)
          );
        }
      },
    });
    ReactTestUtils.renderIntoDocument(<MockComponent depth={0} count={2} />);
    expect(updates).toEqual([0, 1, 2]);
    ReactUpdates.batchedUpdates(function() {