static makeSubItems(entity, urlSummaries) {
    urlSummaries = urlSummaries.filter(s => s.entity === entity);
    return urlSummaries.filter(s => s.entity === entity)
      .map(s => ({
        url: s.url,
        mainThreadTime: s.mainThreadTime,
        transferSize: s.transferSize,
      }))
      // Sort by main thread time first, then transfer size to break ties.
      .sort((a, b) => (b.mainThreadTime - a.mainThreadTime) || (b.transferSize - a.transferSize));
  }
@param {LH.Artifacts.Entity} entity
@param {import('@paulirish/trace_engine/models/trace/extras/ThirdParties.js').URLSummary[]} urlSummaries
@return {URLSummary[]}