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".
value: undefined,
        children: '' + initialValue,
      });
    } else if (tag === 'select') {
      if (__DEV__) {
        ReactControlledValuePropTypes.checkPropTypes(
          'select',
          props,
          () => '', 
        );
        for (var i = 0; i < valuePropNames.length; i++) {
          var propName = valuePropNames[i];
          if (props[propName] == null) {
            continue;
          }
          var isArray = Array.isArray(props[propName]);
          if (props.multiple && !isArray) {
            warning(
              false,
              'The `%s` prop supplied to <select> must be an array if ' +
                '`multiple` is true.%s',
              propName,
              '', 
            );
          } else if (!props.multiple && isArray) {
            warning(
              false,
              'The `%s` prop supplied to <select> must be a scalar ' +
                'value if `multiple` is false.%s',
              propName,