Helper function that recursively discovers the configured size for a
given renderNode.
function _resolveConfigSize(renderNode) {
        if (renderNode instanceof RenderNode) {
            var result = null;
            var target = renderNode.get();
            if (target) {
                result = _resolveConfigSize(target);
                if (result) {
                    return result;
                }
            }
            if (renderNode._child) {
                return _resolveConfigSize(renderNode._child);
            }
        }
        else if (renderNode instanceof Surface) {
            return renderNode.size ? {
                renderNode: renderNode,
                size: renderNode.size
            } : undefined;
        }
        else if (renderNode.options && renderNode.options.size) {
            return {
                renderNode: renderNode,
                size: renderNode.options.size
            };
        }
        return undefined;
    }