**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`
it('should reconnect Bare Element to Bare Element', () =>
          expectMarkupMatch(bareElement, bareElement));
      });
      it('should error reconnecting different element types', () =>
        expectMarkupMismatch(<div />, <span />));
      it('should error reconnecting missing attributes', () =>
        expectMarkupMismatch(<div id="foo" />, <div />));
      it('should error reconnecting added attributes', () =>
        expectMarkupMismatch(<div />, <div id="foo" />));
      it('should error reconnecting different attribute values', () =>
        expectMarkupMismatch(<div id="foo" />, <div id="bar" />));
      it('can explicitly ignore errors reconnecting different element types of children', () =>
        expectMarkupMatch(
          <div><div /></div>,
          <div suppressHydrationWarning={true}><span /></div>,
        ));
      it('can explicitly ignore errors reconnecting missing attributes', () =>
        expectMarkupMatch(
          <div id="foo" />,
          <div suppressHydrationWarning={true} />,
        ));
      it('can explicitly ignore errors reconnecting added attributes', () =>
        expectMarkupMatch(
          <div />,
          <div id="foo" suppressHydrationWarning={true} />,
        ));
      it('can explicitly ignore errors reconnecting different attribute values', () =>
        expectMarkupMatch(
          <div id="foo" />,
          <div id="bar" suppressHydrationWarning={true} />,