Since React 16.0.0, it looks like there might be a case where `event.target` on a change event in IE9 reports as the window, but I can't reproduce it outside of the DOM test fixtures.

*Steps to reproduce*

1. Open this build of the fixtures: http://react-ie-9-target-issues.surge.sh in IE9
2. Enter text into an input
3. Observe that the `event.target.value` is the window, as recorded by the fixture

I can not reproduce this using the following CodePen:

https://codepen.io/nhunzaker/pen/dmeoxJ?editors=1010
Viewable in IE9 here: https://s.codepen.io/nhunzaker/debug/dmeoxJ/PNrvYLevqQbM

Here's a diff of my changes with master:
https://github.com/facebook/react/compare/master...nhunzaker:ie9-target-issue

Any idea what's going on? Here's what I think I need to check next:

- [x] Differences in rAF polyfill
- [x] Differences in map/set polyfill

_This list will probably grow_
/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
import {TEXT_NODE} from '../shared/HTMLNodeType';
/**
 * Gets the target node from a native browser event by accounting for
 * inconsistencies in browser DOM APIs.
 *
 * @param {object} nativeEvent Native browser event.
 * @return {DOMEventTarget} Target node.
 */
function getEventTarget(nativeEvent) {
  let target = nativeEvent.target || window;
  
  if (target.correspondingUseElement) {
    target = target.correspondingUseElement;
  }
  
  
  return target.nodeType === TEXT_NODE ? target.parentNode : target;
}
export default getEventTarget;