code: function() {
          var candidates = this.layers || this.map.layers;
          var layers = [];
          var layer;
          for (var i=candidates.length-1; i>=0; --i) {
              layer = candidates[i];
              if (layer instanceof OpenLayers.Layer.UTFGrid ) { 
                  layers.push(layer);
              }
          }
          return layers;
      }
docs: Method: findLayers
  Internal method to get the layers, independent of whether we are
  inspecting the map or using a client-provided array
  
  The default value of this.layers is null; this causes the
  findLayers method to return ALL UTFGrid layers encountered.
  
  Parameters:
  None
  
  Returns:
  {Array} Layers to handle on each event