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 Child2 = React.createClass({
        render: function() {
          return <div>Child2</div>;
        },
      });
      var Child3 = React.createClass({
        render: function() {
          return <div onclick="1">Child3</div>;
        },
      });
      var Child4 = React.createClass({
        render: function() {
          return <div>Child4</div>;
        },
      });
      ReactDOMServer.renderToString(<Parent />, container);
      expect(console.error.calls.count()).toBe(2);
      expect(console.error.calls.argsFor(0)[0]).toContain('className');
      var matches = console.error.calls.argsFor(0)[0].match(/.*\(.*:(\d+)\).*/);
      var previousLine = matches[1];
      expect(console.error.calls.argsFor(1)[0]).toContain('onClick');
      matches = console.error.calls.argsFor(1)[0].match(/.*\(.*:(\d+)\).*/);
      var currentLine = matches[1];
      
      
      expect(parseInt(previousLine, 10) + 12).toBe(parseInt(currentLine, 10));
    });
  });
});