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.
expect(stubStyle.display).toEqual('none');
      expect(stubStyle.fontFamily).toEqual('Arial');
      expect(stubStyle.lineHeight).toEqual('1.2');
      styles.lineHeight = 0.5;
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('none');
      expect(stubStyle.fontFamily).toEqual('Arial');
      expect(stubStyle.lineHeight).toEqual('1.2');
      ReactDOM.render(<div style={undefined} />, container);
      expect(stubStyle.display).toBe('');
      expect(stubStyle.fontFamily).toBe('');
      expect(stubStyle.lineHeight).toBe('');
    });
    it('should throw when mutating style objects', () => {
      var style = {border: '1px solid black'};
      class App extends React.Component {
        state = {style: style};
        render() {
          return <div style={this.state.style}>asd</div>;
        }
      }
      ReactTestUtils.renderIntoDocument(<App />);
      expectDev(() => (style.position = 'absolute')).toThrow();
    });
    it('should warn for unknown prop', () => {
      spyOn(console, 'error');
      var container = document.createElement('div');
      ReactDOM.render(<div foo={() => {}} />, container);
      expectDev(console.error.calls.count(0)).toBe(1);
      expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(