**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`
itThrows(
    `when rendering ${desc} with server string render`,
    () => testFn(serverRender),
    partialMessage,
  );
  itThrows(
    `when rendering ${desc} with clean client render`,
    () => testFn(clientCleanRender),
    partialMessage,
  );
  
  
  itThrows(
    `when rendering ${desc} with client render on top of bad server markup`,
    () =>
      testFn((element, warningCount = 0) =>
        clientRenderOnBadMarkup(element, warningCount - 1),
      ),
    partialMessage,
  );
}
async function testMarkupMatch(serverElement, clientElement, shouldMatch) {