**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`
'a textarea with a value and no onChange/readOnly',
        async render => {
          
          
          const e = await render(<textarea value="foo" />, 1);
          expect(e.getAttribute('value')).toBe(null);
          expect(e.value).toBe('foo');
        },
      );
      itRenders('a textarea with a defaultValue', async render => {
        const e = await render(<textarea defaultValue="foo" />);
        expect(e.getAttribute('value')).toBe(null);
        expect(e.getAttribute('defaultValue')).toBe(null);
        expect(e.value).toBe('foo');
      });
      itRenders('a textarea value overriding defaultValue', async render => {
        const e = await render(
          <textarea value="foo" defaultValue="bar" readOnly={true} />,
          1,
        );
        expect(e.getAttribute('value')).toBe(null);
        expect(e.getAttribute('defaultValue')).toBe(null);
        expect(e.value).toBe('foo');
      });
      itRenders(
        'a textarea value overriding defaultValue no matter the prop order',
        async render => {
          const e = await render(
            <textarea defaultValue="bar" value="foo" readOnly={true} />,
            1,