getBounds(layer) {
		const bounds = layer instanceof TMXLayer ? boundsPool.get() : this.bounds;
		bounds.setMinMax(
			0,
			0,
			this.cols * this.tilewidth,
			this.rows * this.tileheight,
		);
		return bounds;
	}
return the bounding rect for this map renderer
@param {TMXLayer} [layer] - calculate the bounding rect for a specific layer (will return a new bounds object)
@returns {Bounds}