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.
getDefaultPropsWasCalled = true;
        return {};
      }
      render() {
        return <span className="foo" />;
      }
    }
    test(<Foo />, 'SPAN', 'foo');
    expect(getInitialStateWasCalled).toBe(false);
    expect(getDefaultPropsWasCalled).toBe(false);
    if (__DEV__) {
      expect(console.error.calls.count()).toBe(4);
      expect(console.error.calls.argsFor(0)[0]).toContain(
        'getInitialState was defined on Foo, a plain JavaScript class.',
      );
      expect(console.error.calls.argsFor(1)[0]).toContain(
        'getDefaultProps was defined on Foo, a plain JavaScript class.',
      );
      expect(console.error.calls.argsFor(2)[0]).toContain(
        'propTypes was defined as an instance property on Foo.',
      );
      expect(console.error.calls.argsFor(3)[0]).toContain(
        'contextTypes was defined as an instance property on Foo.',
      );
    }
  });
  it('does not warn about getInitialState() on class components if state is also defined.', () => {
    spyOnDev(console, 'error');
    class Foo extends React.Component {