**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`
'svg child element with a namespace attribute',
        async render => {
          let e = await render(
            <svg><image xlinkHref="http:i.imgur.com/w7GCRPb.png" /></svg>,
          );
          e = e.firstChild;
          expect(e.childNodes.length).toBe(0);
          expect(e.tagName).toBe('image');
          expect(e.namespaceURI).toBe('http:www.w3.org/2000/svg');
          expect(e.getAttributeNS('http:www.w3.org/1999/xlink', 'href')).toBe(
            'http:i.imgur.com/w7GCRPb.png',
          );
        },
      );
      itRenders('svg child element with a badly cased alias', async render => {
        let e = await render(
          <svg><image xlinkhref="http:i.imgur.com/w7GCRPb.png" /></svg>,
          1,
        );
        e = e.firstChild;
        expect(e.hasAttributeNS('http:www.w3.org/1999/xlink', 'href')).toBe(
          false,
        );
        expect(e.getAttribute('xlinkhref')).toBe(
          'http:i.imgur.com/w7GCRPb.png',
        );
      });
      itRenders('svg element with a tabIndex attribute', async render => {
        let e = await render(<svg tabIndex="1" />);
        expect(e.tabIndex).toBe(1);