I think maybe we should revert https://github.com/facebook/react/pull/5947.

People already think `proxyEvent` is some kind of an API: https://github.com/facebook/react/issues/12169.

It's also annoying to view in the debugger because none of the properties show up.

Instead, we could seal the event object or something like that.
}
    if (__DEV__) {
      Object.defineProperty(
        this,
        'nativeEvent',
        getPooledWarningPropertyDefinition('nativeEvent', null),
      );
      Object.defineProperty(
        this,
        'preventDefault',
        getPooledWarningPropertyDefinition('preventDefault', () => {}),
      );
      Object.defineProperty(
        this,
        'stopPropagation',
        getPooledWarningPropertyDefinition('stopPropagation', () => {}),
      );
    }
  },
});
SyntheticEvent.Interface = EventInterface;
/**
 * Helper to reduce boilerplate when creating subclasses.
 */
SyntheticEvent.extend = function(Interface) {
  const Super = this;
  const E = function() {};
  E.prototype = Super.prototype;
  const prototype = new E();
  function Class() {