<s>I'm going to revert</s> I have reverted https://github.com/facebook/react/pull/5947 because it's [very confusing](https://mobile.twitter.com/ReactStudent/status/1018749513572368384) to see Proxies in the console. The warning is just not worth the debugging impediment.

In the future, we should consider sealing or preventing extensions to pooled events (if we're not getting rid of pooling altogether, that is). But that would be a breaking change.
const action = isFunction ? 'setting the method' : 'setting the property';
    warn(action, 'This is effectively a no-op');
    return val;
  }
  function get() {
    const action = isFunction
      ? 'accessing the method'
      : 'accessing the property';
    const result = isFunction
      ? 'This is a no-op function'
      : 'This is set to null';
    warn(action, result);
    return getVal;
  }
  function warn(action, result) {
    const warningCondition = false;
    warningWithoutStack(
      warningCondition,
      "This synthetic event is reused for performance reasons. If you're seeing this, " +
        "you're %s `%s` on a released/nullified synthetic event. %s. " +
        'If you must keep the original synthetic event around, use event.persist(). ' +
        'See https://fb.me/react-event-pooling for more information.',
      action,
      propName,
      result,
    );
  }
}
function getPooledEvent(dispatchConfig, targetInst, nativeEvent, nativeInst) {