code: function findChunkFile(chunk, chunkId, outputFilePath) {
    for (let i = 0; i < chunk.files.length; i++) {
      const chunkFile = chunk.files[i];
      let normalizedOutputFilePath = outputFilePath.replace(/^\.\//, '');
      if (!/\.js$/.test(chunkFile)) {
        normalizedOutputFilePath = normalizedOutputFilePath.substr(
          0,
          normalizedOutputFilePath.length - 3
        );
      }
  
      if (normalizedOutputFilePath === chunkFile) {
        return chunkFile;
      }
    }
    if (chunk.id === chunkId) {
      return chunk.files[0];
    }
    return undefined; // eslint-disable-line no-undefined
  }
docs: Find the filename of a chunk which matches either the id or path provided.
  
  @param {!Chunk} chunk
  @param {number} chunkId
  @param {string} outputFilePath
  @return {string|undefined}