**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`
getChildContext() {
          return {text: this.props.text};
        }
        render() {
          return this.props.children;
        }
      }
      Parent.childContextTypes = {text: PropTypes.string};
      PurpleContext = props => <Parent text="purple">{props.children}</Parent>;
      RedContext = props => <Parent text="red">{props.children}</Parent>;
    });
    itRenders('class child with context', async render => {
      class ClassChildWithContext extends React.Component {