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.
expectDev(console.error.calls.count()).toBe(1);
        expectDev(console.error.calls.argsFor(0)[0]).toContain(
          'A component is using shady DOM. Using shady DOM with React can ' +
            'cause things to break subtly.',
        );
        mountComponent({is: 'custom-shady-div2'});
        expectDev(console.error.calls.count()).toBe(1);
      } finally {
        document.createElement = defaultCreateElement;
      }
    });
    it('should treat menuitem as a void element but still create the closing tag', () => {
      
      spyOn(console, 'error');
      var container = document.createElement('div');
      var returnedValue = ReactDOMServer.renderToString(
        <menu><menuitem /></menu>,
      );
      expect(returnedValue).toContain('</menuitem>');
      expect(function() {
        ReactDOM.render(<menu><menuitem>children</menuitem></menu>, container);
      }).toThrowError(
        'menuitem is a void element tag and must neither have `children` nor use ' +
          '`dangerouslySetInnerHTML`.',
      );
    });
    it('should validate against multiple children props', () => {
      expect(function() {
        mountComponent({children: '', dangerouslySetInnerHTML: ''});
      }).toThrowError(