function cloneWithProps(child, props) {
  if ("production" !== process.env.NODE_ENV) {
    ("production" !== process.env.NODE_ENV ? warning(
      !child.ref,
      'You are calling cloneWithProps() on a child with a ref. This is ' +
      'dangerous because you\'re creating a new child which will not be ' +
      'added as a ref to its parent.'
    ) : null);
  }

  var newProps = ReactPropTransferer.mergeProps(props, child.props);

  // Use `child.props.children` if it is provided.
  if (!newProps.hasOwnProperty(CHILDREN_PROP) &&
      child.props.hasOwnProperty(CHILDREN_PROP)) {
    newProps.children = child.props.children;
  }

  // The current API doesn't retain _owner and _context, which is why this
  // doesn't use ReactElement.cloneAndReplaceProps.
  return ReactElement.createElement(child.type, newProps);
}
Sometimes you want to change the props of a child passed to you. Usually
this is to add a CSS class.

@param {object} child child component you'd like to clone
@param {object} props props you'd like to modify. They will be merged
as if you used `transferPropsTo()`.
@return {object} a clone of child with props merged in.