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

'componentWillReceiveProps' |
  'shouldComponentUpdate' |
  'componentWillUpdate' |
  'componentDidUpdate' |
  'componentDidMount';
type Measurement = {
  timerType: TimerType,
  instanceID: DebugID,
  duration: number,
};
type TreeSnapshot = {
  [key: DebugID]: {
    displayName: string,
    text: string,
    updateCount: number,
    childIDs: Array<DebugID>,
    ownerID: DebugID,
    parentID: DebugID,
  }
};
type HistoryItem = {
  duration: number,
  measurements: Array<Measurement>,
  operations: Array<Operation>,
  treeSnapshot: TreeSnapshot,
};
export type FlushHistory = Array<HistoryItem>;
var hooks = [];
var didHookThrowForEvent = {};
function callHook(event, fn, context, arg1, arg2, arg3, arg4, arg5) {