**Do you want to request a *feature* or report a *bug*?**
Bug

**What is the current behavior?**
I've started recieving this warning about my SVGs which is using [feGaussianBlur](https://developer.mozilla.org/en-US/docs/Web/SVG/Element/feGaussianBlur): 
`Warning: Expected server HTML to contain a matching <feGaussianBlur> in <filter>.`

**What is the expected behavior?**
Should be no warnings because there are no difference.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Such behavior started right after updating to `React 16.0.0-rc.3` and never happened with `React 15.6.1`
/**
 * 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.
 *
 * @emails react-core
 */
'use strict';
let ExecutionEnvironment;
let PropTypes;
let React;
let ReactDOM;
let ReactDOMServer;
let ReactTestUtils;
const stream = require('stream');
const TEXT_NODE_TYPE = 3;
function asyncReactDOMRender(reactElement, domElement, forceHydrate) {
  return new Promise(resolve => {
    if (forceHydrate) {
      ReactDOM.hydrate(reactElement, domElement);
    } else {
      ReactDOM.render(reactElement, domElement);
    }
    
    
    resolve();
  });
}
async function expectErrors(fn, count) {