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.
 *
 * @flow
 */
import type {ReactElement} from 'shared/ReactElementType';
import React from 'react';
import emptyFunction from 'fbjs/lib/emptyFunction';
import emptyObject from 'fbjs/lib/emptyObject';
import hyphenateStyleName from 'fbjs/lib/hyphenateStyleName';
import invariant from 'fbjs/lib/invariant';
import memoizeStringOnly from 'fbjs/lib/memoizeStringOnly';
import warning from 'fbjs/lib/warning';
import checkPropTypes from 'prop-types/checkPropTypes';