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.
});
    it('should update styles if updated to null multiple times', () => {
      var styles = null;
      var container = document.createElement('div');
      ReactDOM.render(<div style={styles} />, container);
      styles = {display: 'block'};
      var stubStyle = container.firstChild.style;
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
      ReactDOM.render(<div style={null} />, container);
      expect(stubStyle.display).toEqual('');
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
      ReactDOM.render(<div style={null} />, container);
      expect(stubStyle.display).toEqual('');
    });
    it('should allow named slot projection on both web components and regular DOM elements', () => {
      var container = document.createElement('div');
      ReactDOM.render(
        <my-component>
          <my-second-component slot="first" />
          <button slot="second">Hello</button>
        </my-component>,
        container,
      );
      var lightDOM = container.firstChild.childNodes;
      expect(lightDOM[0].getAttribute('slot')).toBe('first');
      expect(lightDOM[1].getAttribute('slot')).toBe('second');
    });
    it('should skip reserved props on web components', () => {