We should be warning if a controlled component becomes uncontrolled, or vice versa.

I thought this was fixed in https://github.com/facebook/react/issues/5821, but apparently it was either not fixed for checkbox components, or maybe I subsequently broke it in https://github.com/facebook/react/pull/7003 (or similar).  Regardless, we should fix it.

Demo of case that should warn: https://jsfiddle.net/s4742gkk/

render() {
        return (
          <div>
            <input
              ref="a"
              type="radio"
              name="fruit"
              checked={true}
              onChange={emptyFunction}
            />A
            <input
              ref="b"
              type="radio"
              name="fruit"
              onChange={emptyFunction}
            />B
            <form>
              <input
                ref="c"
                type="radio"
                name="fruit"
                defaultChecked={true}
                onChange={emptyFunction}
              />
            </form>
          </div>