code: public String getIconUrl(String size) {
          if (iconUrl == null) {
              return Jenkins.RESOURCE_PATH + "/images/" + size + "/" + HEALTH_UNKNOWN_IMG;
          }
          if (iconUrl.startsWith("/")) {
              return iconUrl.replace("/32x32/", "/" + size + "/");
          }
          return Jenkins.RESOURCE_PATH + "/images/" + size + "/" + iconUrl;
      }
docs: Get's the iconUrl relative to the hudson root url, for the correct size.
  
  @param size The size, e.g. 32x32, 24x24 or 16x16.
  @return The url relative to hudson's root url.