code: 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;
      }
docs: Helper function that recursively discovers the configured size for a
  given renderNode.