code: function() {
                  var mapping = this._getResourceColorIndexMapping();
                  var used = [],
                      resource;
  
                  for (resource in mapping) {
                      if (Object.prototype.hasOwnProperty.call(mapping, resource)) {
                          used.push(resource);
                      }
                  }
  
                  return used;
              }
docs: 获得已使用的资源的列表
  
  @return {Array}