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

if (currentFlushNesting === 0) {
    return;
  }
  if (currentTimerType !== timerType && !lifeCycleTimerHasWarned) {
    warning(
      false,
      'There is an internal error in the React performance measurement code. ' +
      'We did not expect %s timer to stop while %s timer is still in ' +
      'progress for %s instance. Please report this as a bug in React.',
      timerType,
      currentTimerType || 'no',
      (debugID === currentTimerDebugID) ? 'the same' : 'another'
    );
    lifeCycleTimerHasWarned = true;
  }
  if (isProfiling) {
    currentFlushMeasurements.push({
      timerType,
      instanceID: debugID,
      duration: performanceNow() - currentTimerStartTime - currentTimerNestedFlushDuration,
    });
  }
  currentTimerStartTime = 0;
  currentTimerNestedFlushDuration = 0;
  currentTimerDebugID = null;
  currentTimerType = null;
}
function pauseCurrentLifeCycleTimer() {