My application crashes IE9 when I upgrade to React v15.2.0! It works fine with v15.1.0 and all earlier versions.

My diff looks like this

```
package.json
 -    "react-addons-perf": "15.1.0",
 +    "react-addons-perf": "15.2.0",
 -    "react-addons-shallow-compare": "15.1.0",
 +    "react-addons-shallow-compare": "15.2.0",
 -    "react-addons-test-utils": "15.1.0",
 +    "react-addons-test-utils": "15.2.0",
 -    "react": "15.1.0",
 +    "react": "15.2.0",
 -    "react-addons-css-transition-group": "15.1.0",
 +    "react-addons-css-transition-group": "15.2.0",
 -    "react-addons-transition-group": "15.1.0",
 +    "react-addons-transition-group": "15.2.0",
 -    "react-dom": "15.1.0",
 +    "react-dom": "15.2.0",
```

Below is a GIF of the crash, I recorded this using BrowserStack (Win7, IE9). I start the recording with Google loaded and dev tools open, I then navigated to my apps URL. As you can see IE9 just crashes hard with nothing logged to console. All other browsers load my app just fine, this only seems to crash IE9!

![crash](https://cloud.githubusercontent.com/assets/456400/18810916/7694bfd0-829a-11e6-897d-4b70df1972a2.gif)

Did you guys drop support for IE9 in 15.2.0? If not, any ideas what might be causing this?

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactDOMComponentTree
 */
'use strict';
var DOMProperty = require('DOMProperty');
var ReactDOMComponentFlags = require('ReactDOMComponentFlags');
var invariant = require('invariant');
var ATTR_NAME = DOMProperty.ID_ATTRIBUTE_NAME;
var Flags = ReactDOMComponentFlags;
var internalInstanceKey =
  '__reactInternalInstance$' + Math.random().toString(36).slice(2);
/**
 * Drill down (through composites and empty components) until we get a host or
 * host text component.
 *
 * This is pretty polymorphic but unavoidable with the current structure we have
 * for `_renderedChildren`.
 */
function getRenderedHostOrTextFromComponent(component) {