Version: **15.0.0-rc.1**
Fiddle: https://jsfiddle.net/69z2wepo/33980/ (check console)

For an example providing `NaN` to a css property will result in "_NaN is an invalid value for the fontSize css style property_".
Now I'm aware that there is an error in my code but I have no idea which component I should check.
I would like to have something like this: "_NaN is an invalid value for the fontSize style property. Check the render method of Header_".
I'll be happy to try to solve this if this is something we want to do.

ReactDOM.render(
        <div>
          <div key="one">
            <div key="A">A</div><div key="B">B</div>
          </div>
          <div key="two">
            <div key="C">C</div><div key="D">D</div>
          </div>
        </div>,
        container
      );
      
      ReactDOM.render(
        <div>
          <div key="one">
            <div key="B">B</div><div key="A">A</div>
          </div>
          <div key="two">
            <div key="D">D</div><div key="C">C</div>
          </div>
        </div>,
        container
      );
      expect(container.textContent).toBe('BADC');
    });
  });
  describe('createOpenTagMarkup', function() {
    var genMarkup;
    function quoteRegexp(str) {