**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`
<div id="parent"><div id="child1" />      <div id="child2" /></div>, 
        ));
      it('should error reconnecting a div with children separated by different whitespace on the server', () =>
        expectMarkupMismatch(
          
          <div id="parent"><div id="child1" />      <div id="child2" /></div>, 
          <div id="parent"><div id="child1" /><div id="child2" /></div>,
        ));
      it('should error reconnecting a div with children separated by different whitespace', () =>
        expectMarkupMismatch(
          <div id="parent"><div id="child1" /> <div id="child2" /></div>,
          
          <div id="parent"><div id="child1" />      <div id="child2" /></div>, 
        ));
      it('can distinguish an empty component from a dom node', () =>
        expectMarkupMismatch(
          <div><span /></div>,
          <div><EmptyComponent /></div>,
        ));
      it('can distinguish an empty component from an empty text component', () =>
        expectMarkupMatch(<div><EmptyComponent /></div>, <div>{''}</div>));
      it('can explicitly ignore reconnecting more children', () =>
        expectMarkupMatch(
          <div><div /></div>,
          <div suppressHydrationWarning={true}><div /><div /></div>,
        ));
      it('can explicitly ignore reconnecting fewer children', () =>
        expectMarkupMatch(
          <div><div /><div /></div>,