code: function GoogleMapsMapType (layers, engine, map) {
    this._layers = layers;
    this._engine = engine;
    this._map = map;
  
    this._hoveredLayers = [];
  
    this.tileSize = new google.maps.Size(256, 256);
    this._internalView = new GMapsCartoDBLayerGroupView(this._engine._cartoLayerGroup, {
      nativeMap: map
    });
    this._id = this._internalView._id;
    this._internalView.on('featureClick', this._onFeatureClick, this);
    this._internalView.on('featureOver', this._onFeatureOver, this);
    this._internalView.on('featureOut', this._onFeatureOut, this);
    this._internalView.on('featureError', this._onFeatureError, this);
  }
docs: This object is a custom Google Maps MapType to enable feature interactivity
  using an internal GMapsCartoDBLayerGroupView instance.
  
  NOTE: It also contains the feature events handlers. That's why it requires the carto layers array.