We used to throw if event listener is not a function in Stack:

```js
ReactDOM.render(
  <h1 onClick={{}}>Hello World!</h1>,
  document.getElementById('container')
);
```

<img width="565" alt="screen shot 2017-08-08 at 3 41 08 pm" src="https://user-images.githubusercontent.com/810438/29077502-2646412e-7c50-11e7-8c99-3b7f6c0a2589.png">

Fiber silently ignores this.

I think we should throw. This would let us add support for objects (e.g. for passive listener configuration) if we want to in a minor rather than a major.
'&#x27;&quot;&lt;&gt;&amp;' +
          '</div>',
      );
    });
  });
  describe('unmountComponent', () => {
    
    if (!ReactDOMFeatureFlags.useFiber) {
      it('should clean up input value tracking', () => {
        var container = document.createElement('div');
        var node = ReactDOM.render(
          <input type="text" defaultValue="foo" />,
          container,
        );
        var tracker = inputValueTracking._getTrackerFromNode(node);
        spyOn(tracker, 'stopTracking');
        ReactDOM.unmountComponentAtNode(container);
        expect(tracker.stopTracking.calls.count()).toBe(1);
      });
      it('should clean up input textarea tracking', () => {
        var container = document.createElement('div');
        var node = ReactDOM.render(<textarea defaultValue="foo" />, container);
        var tracker = inputValueTracking._getTrackerFromNode(node);
        spyOn(tracker, 'stopTracking');
        ReactDOM.unmountComponentAtNode(container);
        expect(tracker.stopTracking.calls.count()).toBe(1);
      });
    }
    it('unmounts children before unsetting DOM node info', () => {
      class Inner extends React.Component {