*feature*

>Warning: A component is `contentEditable` and contains `children` managed by React. It is now your responsibility to guarantee that none of those nodes are unexpectedly modified or duplicated. This is probably not intentional.

It would help heaps if I would know _which_ component is causing this.
render() {
            return <polymer-component />;
          }
        }
        var node = document.createElement('div');
        ReactDOM.render(<ShadyComponent />, node);
        expectDev(console.error.calls.count()).toBe(1);
        expectDev(console.error.calls.argsFor(0)[0]).toContain(
          'ShadyComponent is using shady DOM. Using shady DOM with React can ' +
            'cause things to break subtly.',
        );
        mountComponent({is: 'custom-shady-div2'});
        expectDev(console.error.calls.count()).toBe(1);
      } finally {
        document.createElement = defaultCreateElement;
      }
    });
    it('should emit a warning once for an unnamed custom component using shady DOM', () => {