@sebmarkbage Has pointed out that `renderComponent` can get used in non-DOM situations (eg, we use it for some `<canvas>` rendering where the container is not the canvas). Can you move this invariant into `ReactComponent#_mountComponentIntoNode` (https://github.com/facebook/react/blob/master/src/core/ReactComponent.js#L514)? That will ensure we're only doing this for DOMish components.