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.
var fakeNativeEvent = {};
        ReactTestUtils.simulateNativeEventOnNode(
          'topClick',
          target,
          fakeNativeEvent,
        );
      }
      click(node);
      expect(ops).toEqual(['A']);
      ops = [];
      
      inst.flip();
      click(node);
      expect(ops).toEqual(['B']);
      ops = [];
      
      inst.tick();
      click(node);
      expect(ops).toEqual(['B']);
      ops = [];
      
      
      
      
      ReactDOM.render(
        [<Example key="a" forceA={true} />, <Click key="b" />],