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

emitEvent('onEndProcessingChildContext');
  },
  onHostOperation(operation: Operation) {
    checkDebugID(operation.instanceID);
    emitEvent('onHostOperation', operation);
  },
  onSetState(): void {
    emitEvent('onSetState');
  },
  onSetChildren(debugID: DebugID, childDebugIDs: Array<DebugID>) {
    checkDebugID(debugID);
    childDebugIDs.forEach(checkDebugID);
    emitEvent('onSetChildren', debugID, childDebugIDs);
  },
  onBeforeMountComponent(debugID: DebugID, element: ReactElement, parentDebugID: DebugID): void {
    checkDebugID(debugID);
    checkDebugID(parentDebugID, true);
    emitEvent('onBeforeMountComponent', debugID, element, parentDebugID);
    markBegin(debugID, 'mount');
  },
  onMountComponent(debugID: DebugID): void {
    checkDebugID(debugID);
    markEnd(debugID, 'mount');
    emitEvent('onMountComponent', debugID);
  },
  onBeforeUpdateComponent(debugID: DebugID, element: ReactElement): void {
    checkDebugID(debugID);
    emitEvent('onBeforeUpdateComponent', debugID, element);
    markBegin(debugID, 'update');
  },