**Do you want to request a *feature* or report a *bug*?**
bug

**What is the current behavior?**
In normal rendering, you can memoize a class-based component: https://jsfiddle.net/586ea3cx/

With the shallow renderer, it seems like you can't: https://jsfiddle.net/odj217Lv/1/

This might be blocking https://github.com/airbnb/enzyme/pull/1914, in which tests are failing with `Cannot call a class as a function`. (it's tough to repro stuff with the shallow renderer)
UNSAFE_componentWillMount = logger('componentWillMount');
      componentDidMount = logger('componentDidMount');
      UNSAFE_componentWillReceiveProps = logger('componentWillReceiveProps');
      shouldComponentUpdate = logger('shouldComponentUpdate');
      UNSAFE_componentWillUpdate = logger('componentWillUpdate');
      componentDidUpdate = logger('componentDidUpdate');
      componentWillUnmount = logger('componentWillUnmount');
      render() {