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

},
  removeHook(hook: Hook): void {
    for (var i = 0; i < hooks.length; i++) {
      if (hooks[i] === hook) {
        hooks.splice(i, 1);
        i--;
      }
    }
  },
  isProfiling(): boolean {
    return isProfiling;
  },
  beginProfiling(): void {
    if (isProfiling) {
      return;
    }
    isProfiling = true;
    flushHistory.length = 0;
    resetMeasurements();
    ReactDebugTool.addHook(ReactHostOperationHistoryHook);
  },
  endProfiling(): void {
    if (!isProfiling) {
      return;
    }
    isProfiling = false;
    resetMeasurements();
    ReactDebugTool.removeHook(ReactHostOperationHistoryHook);
  },
  getFlushHistory(): FlushHistory {