code: function (color, imageurl, otherparams) {
              var fullUrl = "";
              var gifUrl = "";
  
              if (imageurl) {
                  var imageFullUrl = /^(data|https?):/i.test(imageurl) ? imageurl : this.getSkinImageFullUrl(imageurl);
                  fullUrl = "url(" + imageFullUrl + ") ";
  
                  if (ariaUtilsString.endsWith(imageurl, ".png")) {
                      gifUrl = imageFullUrl.substring(0, imageFullUrl.length - 4) + ".gif";
                  } else {
                      gifUrl = imageFullUrl;
                  }
              }
  
              var rule = ["background: ", color, " ", fullUrl, otherparams, ";"];
              if (gifUrl) {
                  rule.push("_background-image: url(", gifUrl, ") !important;");
              }
  
              return rule.join("");
          }
docs: Build the backgroung rule of a CSS selector. It is equivalent to the background macro inside .ftl files. It
  computes the path to the css image from the baseUrl FIXME This function is needed because the packager
  modifies any url(
  @param {String} color Color description
  @param {String} imageurl Image path, relative to the css folder
  @param {String} otherparams Extra parameters
  @return {String} full background rule