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. 
return <div>{context.text}</div>;
      }
      Grandchild.contextTypes = {text: PropTypes.string};
      const Child = props => <Grandchild />;
      const e = await render(<PurpleContext><Child /></PurpleContext>);
      expect(e.textContent).toBe('purple');
    });
    itRenders('a child context overriding a parent context', async render => {
      const Grandchild = (props, context) => {
        return <div>{context.text}</div>;
      };
      Grandchild.contextTypes = {text: PropTypes.string};
      const e = await render(
        <PurpleContext><RedContext><Grandchild /></RedContext></PurpleContext>,
      );
      expect(e.textContent).toBe('red');
    });
    itRenders('a child context merged with a parent context', async render => {
      class Parent extends React.Component {
        getChildContext() {
          return {text1: 'purple'};
        }
        render() {
          return <Child />;
        }
      }
      Parent.childContextTypes = {text1: PropTypes.string};
      class Child extends React.Component {