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.
expect((<any>console.error).calls.argsFor(1)[0]).toContain(
        'getDefaultProps was defined on ClassicProperties, ' +
        'a plain JavaScript class.'
      );
      expect((<any>console.error).calls.argsFor(2)[0]).toContain(
        'propTypes was defined as an instance property on ClassicProperties.'
      );
      expect((<any>console.error).calls.argsFor(3)[0]).toContain(
        'contextTypes was defined as an instance property on ClassicProperties.'
      );
    }
  });
  it('does not warn about getInitialState() on class components ' +
     'if state is also defined.', () => {
    spyOnDev(console, 'error');
    class Example extends React.Component {
      state = {};
      getInitialState() {
        return {};
      }
      render() {
        return React.createElement('span', {className: 'foo'});
      }
    }
    test(React.createElement(Example), 'SPAN', 'foo');
    if (__DEV__) {
      expect((<any>console.error).calls.count()).toBe(0);
    }
  });
  it('should warn when misspelling shouldComponentUpdate', function() {