`BoundedStatValueSummary.WriteSummaryData` in PerfReportTool expects the input CSV to contain a `frametime` stat even if `frametime` is not actually used explicitly in the summary XML definition, and report generation will fail if the CSV does not contain a stat with that name. I happened to trigger this case since I am filtering/preprocessing CSVs and removing that stat.
This restriction seems to be unnecessary: `frametime` is used to calculate some formulas but not all of them, and a summary might only contain min/max/unweighted averages which do not need it (which is my case). It would be better to only trigger an error if `frametime` is absent and one of the formulas which need it is used.