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.
}
    }
    if (__DEV__) {
      validatePropertiesInDevelopment(tag, props);
    }
    assertValidProps(tag, props, getStackAddendum);
    var out = createOpenTagMarkup(
      element.type,
      tag,
      props,
      namespace,
      this.makeStaticMarkup,
      this.stack.length === 1,
    );
    var footer = '';
    if (omittedCloseTags.hasOwnProperty(tag)) {
      out += '/>';
    } else {
      out += '>';
      footer = '</' + element.type + '>';
    }
    var children;
    var innerMarkup = getNonChildrenInnerMarkup(props);
    if (innerMarkup != null) {
      children = [];
      if (newlineEatingTags[tag] && innerMarkup.charAt(0) === '\n') {