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. 
render() {
              return {x: 123};
            }
          }
          await render(<ObjectComponent />, 1);
        },
        'Objects are not valid as a React child (found: object with keys ' +
          '{x}). If you meant to render a collection of children, use ' +
          'an array instead.',
      );
      itThrowsWhenRendering(
        'top-level object',
        async render => {
          await render({x: 123});
        },
        'Objects are not valid as a React child (found: object with keys ' +
          '{x}). If you meant to render a collection of children, use ' +
          'an array instead.',
      );
    });
  });
  describe('form controls', function() {
    describe('inputs', function() {
      itRenders('an input with a value and an onChange', async render => {
        const e = await render(<input value="foo" onChange={() => {}} />);
        expect(e.value).toBe('foo');
      });