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.
domElement,
        );
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topLoad',
          'load',
          domElement,
        );
        break;
      case 'form':
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topReset',
          'reset',
          domElement,
        );
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topSubmit',
          'submit',
          domElement,
        );
        break;
      case 'details':
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topToggle',
          'toggle',
          domElement,
        );
        break;
      case 'input':
        ReactDOMFiberInput.initWrapperState(domElement, rawProps);
        ReactBrowserEventEmitter.trapBubbledEvent(