**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`
if (console.error.calls && console.error.calls.reset) {
    console.error.calls.reset();
  } else {
    spyOn(console, 'error');
  }
  const result = await fn();
  if (
    console.error.calls.count() !== count &&
    console.error.calls.count() !== 0
  ) {
    console.log(
      `We expected ${count} warning(s), but saw ${console.error.calls.count()} warning(s).`,
    );
    if (console.error.calls.count() > 0) {
      console.log(`We saw these warnings:`);
      for (var i = 0; i < console.error.calls.count(); i++) {
        console.log(console.error.calls.argsFor(i)[0]);
      }
    }
  }
  expectDev(console.error.calls.count()).toBe(count);
  return result;
}
function renderIntoDom(reactElement, domElement, forceHydrate, errorCount = 0) {