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 ownerDocument: Document = rootContainerElement.nodeType ===
      DOCUMENT_NODE
      ? (rootContainerElement: any)
      : rootContainerElement.ownerDocument;
    var domElement: Element;
    var namespaceURI = parentNamespace;
    if (namespaceURI === HTML_NAMESPACE) {
      namespaceURI = getIntrinsicNamespace(type);
    }
    if (__DEV__) {
      var isCustomComponentTag = isCustomComponent(type, props);
    }
    if (namespaceURI === HTML_NAMESPACE) {
      if (__DEV__) {
        
        
        warning(
          isCustomComponentTag || type === type.toLowerCase(),
          '<%s /> is using uppercase HTML. Always use lowercase HTML tags ' +
            'in React.',
          type,
        );
      }
      if (type === 'script') {
        
        
        var div = ownerDocument.createElement('div');
        div.innerHTML = '<script><' + '/script>';