addChunk(name) {
		if (name) {
			const chunk = this.namedChunks.get(name);
			if (chunk !== undefined) {
				return chunk;
			}
		}
		const chunk = new Chunk(name, this._backCompat);
		this.chunks.add(chunk);
		if (this._backCompat)
			ChunkGraph.setChunkGraphForChunk(chunk, this.chunkGraph);
		if (name) {
			this.namedChunks.set(name, chunk);
		}
		return chunk;
	}
This method first looks to see if a name is provided for a new chunk,
and first looks to see if any named chunks already exist and reuse that chunk instead.
@param {ChunkName=} name optional chunk name to be provided
@returns {Chunk} create a chunk (invoked during seal event)