**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`
const clientRenderOnBadMarkup = async (element, errorCount = 0) => {
  
  var domElement = document.createElement('div');
  domElement.innerHTML =
    '<div id="badIdWhichWillCauseMismatch" data-reactroot="" data-reactid="1"></div>';
  await renderIntoDom(element, domElement, true, errorCount + 1);
  
  var hydratedTextContent = domElement.textContent;
  
  const cleanDomElement = document.createElement('div');
  ExecutionEnvironment.canUseDOM = true;
  await asyncReactDOMRender(element, cleanDomElement, true);
  ExecutionEnvironment.canUseDOM = false;
  
  const cleanTextContent = cleanDomElement.textContent;
  
  expect(hydratedTextContent).toBe(cleanTextContent);
  
  throw new BadMarkupExpected();
};
function itRenders(desc, testFn) {
  it(`renders ${desc} with server string render`, () => testFn(serverRender));
  it(`renders ${desc} with server stream render`, () => testFn(streamRender));
  itClientRenders(desc, testFn);
}
function itClientRenders(desc, testFn) {