static getMixedContentRow(mixedContentIssues) {
    const requestUrls = new Set();
    for (const issue of mixedContentIssues) {
      const requestUrl = issue.request?.url || issue.mainResourceURL;
      requestUrls.add(requestUrl);
    }
    return {
      issueType: 'Mixed content',
      subItems: {
        type: 'subitems',
        items: Array.from(requestUrls).map(url => ({url})),
      },
    };
  }
@param {Array<LH.Crdp.Audits.MixedContentIssueDetails>} mixedContentIssues
@return {LH.Audit.Details.TableItem}