static computeWaste(stylesheet, networkRecord) {
    const content = stylesheet.content;
    const totalTokenLength = UnminifiedCSS.computeTokenLength(content);

    let url = stylesheet.header.sourceURL;
    if (!url || stylesheet.header.isInline) {
      const contentPreview = UnusedCSS.determineContentPreview(stylesheet.content);
      url = contentPreview;
    }

    const totalBytes = estimateTransferSize(networkRecord, content.length, 'Stylesheet');
    const wastedRatio = 1 - totalTokenLength / content.length;
    const wastedBytes = Math.round(totalBytes * wastedRatio);

    return {
      url,
      totalBytes,
      wastedBytes,
      wastedPercent: 100 * wastedRatio,
    };
  }
@param {LH.Artifacts.CSSStyleSheetInfo} stylesheet
@param {LH.Artifacts.NetworkRequest|undefined} networkRecord
@return {{url: string, totalBytes: number, wastedBytes: number, wastedPercent: number}}