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.
/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @emails react-core
 */
'use strict';
var PropTypes;
var React;
var ReactDOM;
describe('ReactES6Class', () => {
  var container;
  var freeze = function(expectation) {
    Object.freeze(expectation);
    return expectation;
  };
  var Inner;
  var attachedListener = null;
  var renderedName = null;
  beforeEach(() => {
    PropTypes = require('prop-types');
    React = require('react');
    ReactDOM = require('react-dom');
    container = document.createElement('div');
    attachedListener = null;
    renderedName = null;
    Inner = class extends React.Component {
      getName() {