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 previousStartTime = currentFlushStartTime;
  var previousMeasurements = currentFlushMeasurements;
  var previousOperations = ReactHostOperationHistoryHook.getHistory();
  if (currentFlushNesting === 0) {
    currentFlushStartTime = 0;
    currentFlushMeasurements = [];
    clearHistory();
    return;
  }
  if (previousMeasurements.length || previousOperations.length) {
    var registeredIDs = ReactComponentTreeHook.getRegisteredIDs();
    flushHistory.push({
      duration: performanceNow() - previousStartTime,
      measurements: previousMeasurements || [],
      operations: previousOperations || [],
      treeSnapshot: getTreeSnapshot(registeredIDs),
    });
  }
  clearHistory();
  currentFlushStartTime = performanceNow();
  currentFlushMeasurements = [];
}
function checkDebugID(debugID, allowRoot = false) {