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. 
});
      itRenders('a div with a child', async render => {
        const e = await render(<div id="parent"><div id="child" /></div>);
        expect(e.id).toBe('parent');
        expect(e.childNodes.length).toBe(1);
        expect(e.childNodes[0].id).toBe('child');
        expect(e.childNodes[0].childNodes.length).toBe(0);
      });
      itRenders('a div with multiple children', async render => {
        const e = await render(
          <div id="parent"><div id="child1" /><div id="child2" /></div>,
        );
        expect(e.id).toBe('parent');
        expect(e.childNodes.length).toBe(2);
        expect(e.childNodes[0].id).toBe('child1');
        expect(e.childNodes[0].childNodes.length).toBe(0);
        expect(e.childNodes[1].id).toBe('child2');
        expect(e.childNodes[1].childNodes.length).toBe(0);
      });
      itRenders(
        'a div with multiple children separated by whitespace',
        async render => {
          const e = await render(
            <div id="parent"><div id="child1" /> <div id="child2" /></div>,
          );
          expect(e.id).toBe('parent');
          let child1, child2, textNode;
          expect(e.childNodes.length).toBe(3);
          child1 = e.childNodes[0];
          textNode = e.childNodes[1];