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.
ensureListeningTo(rootContainerElement, 'onChange');
        break;
      case 'textarea':
        ReactDOMFiberTextarea.initWrapperState(domElement, rawProps);
        props = ReactDOMFiberTextarea.getHostProps(domElement, rawProps);
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topInvalid',
          'invalid',
          domElement,
        );
        
        
        ensureListeningTo(rootContainerElement, 'onChange');
        break;
      default:
        props = rawProps;
    }
    assertValidProps(tag, props, getCurrentFiberOwnerName);
    setInitialDOMProperties(
      domElement,
      rootContainerElement,
      props,
      isCustomComponentTag,
    );
    switch (tag) {
      case 'input':
        
        
        inputValueTracking.track((domElement: any));
        ReactDOMFiberInput.postMountWrapper(domElement, rawProps);