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. 
<ES6ClassComponent id="foobarbaz" />,
          ));
        it('should reconnect Pure Component to Pure Component', () =>
          expectMarkupMatch(
            <PureComponent id="foobarbaz" />,
            <PureComponent id="foobarbaz" />,
          ));
        it('should reconnect Bare Element to Pure Component', () =>
          expectMarkupMatch(<PureComponent id="foobarbaz" />, bareElement));
        it('should reconnect ES6 Class to Bare Element', () =>
          expectMarkupMatch(bareElement, <ES6ClassComponent id="foobarbaz" />));
        it('should reconnect Pure Component to Bare Element', () =>
          expectMarkupMatch(bareElement, <PureComponent id="foobarbaz" />));
        it('should reconnect Bare Element to Bare Element', () =>
          expectMarkupMatch(bareElement, bareElement));
      });
      it('should error reconnecting different element types', () =>
        expectMarkupMismatch(<div />, <span />));
      it('should error reconnecting missing attributes', () =>
        expectMarkupMismatch(<div id="foo" />, <div />));
      it('should error reconnecting added attributes', () =>
        expectMarkupMismatch(<div />, <div id="foo" />));
      it('should error reconnecting different attribute values', () =>
        expectMarkupMismatch(<div id="foo" />, <div id="bar" />));
    });
    describe('inline styles', function() {
      it('should error reconnecting missing style attribute', () =>
        expectMarkupMismatch(<div style={{width: '1px'}} />, <div />));
      it('should error reconnecting added style attribute', () =>
        expectMarkupMismatch(<div />, <div style={{width: '1px'}} />));