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".
return Component.prototype && Component.prototype.isReactComponent;
}
function getNonChildrenInnerMarkup(props) {
  var innerHTML = props.dangerouslySetInnerHTML;
  if (innerHTML != null) {
    if (innerHTML.__html != null) {
      return innerHTML.__html;
    }
  } else {
    var content = props.children;
    if (typeof content === 'string' || typeof content === 'number') {
      return escapeTextContentForBrowser(content);
    }
  }
  return null;
}
function flattenOptionChildren(children) {