constructor(url, mapId, token) {
    super(url, mapId, token);

    this.tileSize = new google.maps.Size(
        ee.FloatTileOverlay.TILE_EDGE_LENGTH,

        ee.FloatTileOverlay.TILE_EDGE_LENGTH);

    /**
     * The set of loaded floating point buffer tiles. The keys are the
     * coordinates of the tiles, and the values are the corresponding
     * Float32Arrays.
     * @private {goog.structs.Map<!google.maps.Point, Float32Array>}
     */
    this.floatTiles_ = new goog.structs.Map();

    /**
     * The floating point buffer tile DIV elements returned by getTile().
     * The keys are the coordinates of the tiles, and the values are the
     * corresponding DIV elements.
     * @private {goog.structs.Map<!google.maps.Point, !Element>}
     */
    this.floatTileDivs_ = new goog.structs.Map();
  }
@param {string} url The URL for fetching floating point tiles.
@param {string} mapId The map ID for fetching floating point tiles.
@param {string} token The temporary token for fetching tiles.