See the original report in https://github.com/facebook/react/issues/10772#issuecomment-333242375.

The problem is that SVG is case sensitive, and so naïvely setting `tabIndex` and relying on insensitivity won't work with it.

The good news is it seems like `tabindex` is the only valid [SVG attribute](https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute) with this problem. We just missed it because it applies both to HTML and SVG.

I think the fix is to add it back to the whitelist. 
<Footer key={4} />,
      ]);
      let parent = e.parentNode;
      expect(parent.childNodes[0].tagName).toBe('DIV');
      expect(parent.childNodes[1].tagName).toBe('SPAN');
      expect(parent.childNodes[2].tagName).toBe('P');
      expect(parent.childNodes[3].tagName).toBe('H2');
      expect(parent.childNodes[4].tagName).toBe('H3');
    });
    itRenders('a nested array', async render => {
      let e = await render([
        [<div key={1}>text1</div>],
        <span key={1}>text2</span>,
        [[[null, <p key={1} />], false]],
      ]);
      let parent = e.parentNode;
      expect(parent.childNodes[0].tagName).toBe('DIV');
      expect(parent.childNodes[1].tagName).toBe('SPAN');
      expect(parent.childNodes[2].tagName).toBe('P');
    });
    itRenders('an iterable', async render => {
      const threeDivIterable = {
        '@@iterator': function() {
          var i = 0;
          return {
            next: function() {
              if (i++ < 3) {
                return {value: <div key={i} />, done: false};
              } else {
                return {value: undefined, done: true};