**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`
return null;
        }
      };
    });
    describe('elements', function() {
      describe('reconnecting different component implementations', function() {
        let ES6ClassComponent, PureComponent, bareElement;
        beforeEach(() => {
          
          ES6ClassComponent = class extends React.Component {
            render() {
              return <div id={this.props.id} />;
            }
          };
          PureComponent = props => <div id={props.id} />;