The error event on `<source>` elements doesn't work. Looking at #4370, it seems like there is an `onError` for `<video>` but I can't tell if that's supposed to work for `<source>` too.

The error event is useful so I can deduce which format the browser is using.

});
      var container = document.createElement('div');
      ReactDOM.render(<div><Inner /></div>, container);
      ReactDOM.unmountComponentAtNode(container);
    });
  });
  describe('onScroll warning', function() {
    it('should warn about the `onScroll` issue when unsupported (IE8)', () => {
      
      
      jest.resetModuleRegistry()
        .mock('isEventSupported');
      var isEventSupported = require('isEventSupported');
      isEventSupported.mockReturnValueOnce(false);
      var ReactTestUtils = require('ReactTestUtils');
      spyOn(console, 'error');
      ReactTestUtils.renderIntoDocument(<div onScroll={function() {}} />);
      expect(console.error.calls.count()).toBe(1);
      expect(console.error.calls.argsFor(0)[0]).toBe(
        'Warning: This browser doesn\'t support the `onScroll` event'
      );
    });
    it('should not warn when server-side rendering `onScroll`', function() {
      spyOn(console, 'error');
      ReactDOMServer.renderToString(<div onScroll={() => {}}/>);
      expect(console.error).not.toHaveBeenCalled();
    });
  });
  describe('tag sanitization', function() {
    it('should throw when an invalid tag name is used', () => {