**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`
if (render === serverRender || render === streamRender) {
          expect(e.childNodes.length).toBe(1);
          expectTextNode(e.childNodes[0], 'foo');
        } else {
          expect(e.childNodes.length).toBe(2);
          expectTextNode(e.childNodes[0], 'foo');
          expectTextNode(e.childNodes[1], '');
        }
      });
      itRenders('an element with two text children', async render => {
        const e = await render(<div>{'foo'}{'bar'}</div>);
        if (
          render === serverRender ||
          render === clientRenderOnServerString ||
          render === streamRender
        ) {
          
          expect(e.childNodes.length).toBe(3);
          expectTextNode(e.childNodes[0], 'foo');
          expectTextNode(e.childNodes[2], 'bar');
        } else {
          expect(e.childNodes.length).toBe(2);
          expectTextNode(e.childNodes[0], 'foo');
          expectTextNode(e.childNodes[1], 'bar');
        }
      });
      itRenders(
        'a component returning text node between two text nodes',
        async render => {