code: function normalizeResponse(response)
  {
    // if the response doesn't already have a getResponseHeader() method, add one
    if (response && !response.getResponseHeader)
    {
      response.getResponseHeader = function(header)
      {
        return response.headers && response.headers[
                Util.isString(header) ? header.toLowerCase() : header];
      };
    }
  
    return response;
  }
docs: Normalizes the response object so that we can extract response headers from
  it in a uniform way regardless of whether we're using request.js or
  browser-request.js.
  
  @param {Object} response
  
  @return {Object}