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".
while (React.isValidElement(child)) {
    if (__DEV__) {
      pushElementToDebugStack(child);
    }
    var Component = child.type;
    if (typeof Component !== 'function') {
      break;
    }
    var publicContext = processContext(Component, context);
    var inst;
    var queue = [];
    var replace = false;
    var updater = {
      isMounted: function(publicInstance) {
        return false;
      },
      enqueueForceUpdate: function(publicInstance) {
        if (queue === null) {
          warnNoop(publicInstance, 'forceUpdate');
          return null;
        }
      },
      enqueueReplaceState: function(publicInstance, completeState) {
        replace = true;
        queue = [completeState];
      },
      enqueueSetState: function(publicInstance, partialState) {
        if (queue === null) {