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.

);
      expect(console.error.calls.argsFor(1)[0]).toBe(
        'Warning: validateDOMNesting(...): #text cannot appear as a child ' +
        'of <table>. See Foo > table > #text.'
      );
    });
    it('gives useful context in warnings', () => {
      spyOn(console, 'error');
      var Row = React.createClass({
        render: () => <tr />,
      });
      var FancyRow = React.createClass({
        render: () => <Row />,
      });
      var Table = React.createClass({
        render: function() {
          return <table>{this.props.children}</table>;
        },
      });
      var FancyTable = React.createClass({
        render: function() {
          return <Table>{this.props.children}</Table>;
        },
      });
      var Viz1 = React.createClass({
        render: () => <table><FancyRow /></table>,
      });
      var App1 = React.createClass({
        render: () => <Viz1 />,
      });