Observed this on react@16.0.0-beta.5

```js
import React from 'react';
import { renderToString } from 'react-dom/server';

const B = () => 'b';

console.log(renderToString(<div>{'a'}<B />{'c'}</div>));
```

This renders as `<div data-reactroot="">a<!-- -->bc</div>`. If you try to hydrate this you'll get the error: Text content did not match. Server: "bc" Client: "b".
render() {
          return <div ref="myDiv" />;
        }
      }
      const markup = ReactDOMServer.renderToString(<RefsComponent />);
      const root = document.createElement('div');
      root.innerHTML = markup;
      let component = null;
      resetModules();
      await asyncReactDOMRender(
        <RefsComponent ref={e => (component = e)} />,
        root,
        true,
      );
      expect(component.refs.myDiv).toBe(root.firstChild);
    });
  });
  describe('reconnecting to server markup', function() {
    var EmptyComponent;
    beforeEach(() => {
      EmptyComponent = class extends React.Component {
        render() {