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 (!shouldMark(debugID)) {
    return;
  }
  var markName = `${debugID}::${markType}`;
  lastMarkTimeStamp = performanceNow();
  performance.mark(markName);
}
function markEnd(debugID, markType) {
  if (!shouldMark(debugID)) {
    return;
  }
  var markName = `${debugID}::${markType}`;
  var displayName = ReactComponentTreeHook.getDisplayName(debugID) || 'Unknown';
  
  
  
  
  
  
  var timeStamp = performanceNow();
  if (timeStamp - lastMarkTimeStamp > 0.1) {
    var measurementName = `${displayName} [${markType}]`;
    performance.measure(measurementName, markName);
  }
  performance.clearMarks(markName);
  performance.clearMeasures(measurementName);
}
var ReactDebugTool = {
  addHook(hook: Hook): void {
    hooks.push(hook);