function constructAssetToChunkMap(bundle) {
	const assetToChunkMap = new Map();
	for (const fileName in bundle) {
		const chunk = bundle[fileName];
		if (chunk.type !== 'chunk') continue;

		for (const fileId of chunk.referencedFiles) {
			if (!isCssFilename(fileId)) continue;
			let map = assetToChunkMap.get(fileId);
			if (!map) {
				map = {
					isEntry: false,
					isDynamicEntry: false,
					isImplicitEntry: false,
					mergedInto: undefined,
					chunks: []
				};
				assetToChunkMap.set(fileId, map);
			}
			if (chunk.isEntry) {
				map.isEntry = true;
				if (!map.entryChunk) map.entryChunk = fileName;
			}
			if (chunk.isDynamicEntry) map.isDynamicEntry = true;
			if (chunk.isImplicitEntry) map.isImplicitEntry = true;
			const currentIndex = map.chunks.indexOf(fileName);
			if (chunk.implicitlyLoadedBefore && chunk.implicitlyLoadedBefore.length) {
				let index = -1;
				for (const id of chunk.implicitlyLoadedBefore) {
					index = Math.max(index, map.chunks.indexOf(id));
				}
				if (index !== -1) {
					if (index !== currentIndex) {
						map.chunks.splice(currentIndex, 1);
						map.chunks.splice(index, 0, fileName);
					}
					continue;
				}
			}
			if (currentIndex === -1) {
				map.chunks.push(fileName);
			}
		}
	}
	return assetToChunkMap;
}
Generate a mapping of assets to metadata about the chunks that reference them.
@param {Bundle} bundle
@return {Map<string, { isEntry: boolean, isDynamicEntry: boolean, isImplicitEntry: boolean, mergedInto?: string, chunks: string[] }>}