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.
return styleStore.display;
        },
        set display(v) {
          styleStore.display = v;
        },
        get fontFamily() {
          return styleStore.fontFamily;
        },
        set fontFamily(v) {
          styleStore.fontFamily = v;
        },
        get lineHeight() {
          return styleStore.lineHeight;
        },
        set lineHeight(v) {
          styleStore.lineHeight = v;
        },
      };
      var container = document.createElement('div');
      ReactDOM.render(<div style={styles} />, container);
      var stubStyle = container.firstChild.style;
      stubStyle.display = styles.display;
      stubStyle.fontFamily = styles.fontFamily;
      styles.display = 'block';
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('none');
      expect(stubStyle.fontFamily).toEqual('Arial');
      expect(stubStyle.lineHeight).toEqual('1.2');
      styles.fontFamily = 'Helvetica';
      ReactDOM.render(<div style={styles} />, container);