Currently if React is not loaded, ReactDOM shows this:

<img width="664" alt="screen shot 2017-08-08 at 3 36 52 pm" src="https://user-images.githubusercontent.com/810438/29077217-784c7624-7c4f-11e7-88bc-b055407523a9.png">

We should throw a nicer error message in the entry point I think.
ops.push(`Parent:${this.props.step} componentDidMount`);
        }
        componentDidUpdate() {
          ops.push(`Parent:${this.props.step} componentDidUpdate`);
        }
        componentWillUnmount() {
          ops.push(`Parent:${this.props.step} componentWillUnmount`);
        }
        render() {
          const {step} = this.props;
          return [
            <Child key="a" name={`normal[0]:${step}`} />,
            ReactDOM.unstable_createPortal(
              <Child key="b" name={`portal1[0]:${step}`} />,
              portalContainer1,
            ),
            <Child key="c" name={`normal[1]:${step}`} />,
            ReactDOM.unstable_createPortal(
              [
                <Child key="d" name={`portal2[0]:${step}`} />,
                <Child key="e" name={`portal2[1]:${step}`} />,
              ],
              portalContainer2,
            ),
          ];
        }
      }
      ReactDOM.render(<Parent step="a" />, container);
      expect(portalContainer1.innerHTML).toBe('<div>portal1[0]:a</div>');
      expect(portalContainer2.innerHTML).toBe(