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 {Fiber} from './ReactFiber';
import type {ExpirationTime} from './ReactFiberExpirationTime';
import {Update} from 'shared/ReactTypeOfSideEffect';
import {
  debugRenderPhaseSideEffects,
  enableAsyncSubtreeAPI,
} from 'shared/ReactFeatureFlags';
import {isMounted} from 'shared/ReactFiberTreeReflection';
import * as ReactInstanceMap from 'shared/ReactInstanceMap';
import emptyObject from 'fbjs/lib/emptyObject';
import getComponentName from 'shared/getComponentName';