Follow up from https://github.com/facebook/react/pull/11616.

Here's one I found. These two invariants:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L330-L343

are in a function that's behind a DEV block:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L447-L449

I don't think this is intentional, but need to verify.

There may be more. I'll use this issue to track while https://github.com/facebook/react/pull/11616 preserves existing behavior.
getChildContext() {
        return {bar: 'bar-through-context'};
      }
      render() {
        return <Bar />;
      }
    }
    Foo.childContextTypes = {bar: PropTypes.string};
    test(<Foo />, 'DIV', 'bar-through-context');
  });
  it('supports classic refs', () => {
    class Foo extends React.Component {
      render() {
        return <Inner name="foo" ref="inner" />;
      }
    }
    var instance = test(<Foo />, 'DIV', 'foo');
    expect(instance.refs.inner.getName()).toBe('foo');
  });
  it('supports drilling through to the DOM using findDOMNode', () => {
    var instance = test(<Inner name="foo" />, 'DIV', 'foo');
    var node = ReactDOM.findDOMNode(instance);
    expect(node).toBe(container.firstChild);
  });
});