Given the following test case

``` jsx
function TestCmp() {
  return <span>{NaN}</span>;
}

ReactDOM.render(<TestCmp />, document.getElementById('app'));
```

Produces the following warning:

```
Warning: Component's children should not be mutated.
    in span (created by TestCmp)
    in TestCmp (created by Unknown)
```

This is probably caused by [this mutation check](https://github.com/facebook/react/blob/328fc75bc910032ff37dc9d93429fb14b476bd0d/src/renderers/shared/hooks/ReactChildrenMutationWarningHook.js#L34), which was introduced in 15.3.0, but it doesn't work for NaN, because NaN != NaN

var isMutated = false;
  if (Array.isArray(element._shadowChildren)) {
    if (element._shadowChildren.length === element.props.children.length) {
      for (var i = 0; i < element._shadowChildren.length; i++) {
        if (element._shadowChildren[i] !== element.props.children[i]) {
          isMutated = true;
        }
      }
    } else {
      isMutated = true;
    }
  }
  if (!Array.isArray(element._shadowChildren) || isMutated) {
    warning(
      false,
      'Component\'s children should not be mutated.%s',
      ReactComponentTreeHook.getStackAddendumByID(debugID),
    );
  }
}
var ReactChildrenMutationWarningHook = {
  onMountComponent(debugID: DebugID): void {
    handleElement(debugID, ReactComponentTreeHook.getElement(debugID));
  },
  onUpdateComponent(debugID: DebugID): void {
    handleElement(debugID, ReactComponentTreeHook.getElement(debugID));
  },
};
module.exports = ReactChildrenMutationWarningHook;