**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`
render() {
          return <div ref="myDiv" />;
        }
      }
      const markup = ReactDOMServer.renderToString(<RefsComponent />);
      const root = document.createElement('div');
      root.innerHTML = markup;
      let component = null;
      resetModules();
      await asyncReactDOMRender(
        <RefsComponent ref={e => (component = e)} />,
        root,
        true,
      );
      expect(component.refs.myDiv).toBe(root.firstChild);
    });
  });
  describe('reconnecting to server markup', function() {
    var EmptyComponent;
    beforeEach(() => {
      EmptyComponent = class extends React.Component {
        render() {