code: private boolean isTermTrackBreadth(Term t) {
          if (t instanceof TermLengthOrPercent) {
              return true;
          } else if (t instanceof TermIdent) {
              CSSProperty property = genericPropertyRaw(GridTemplateRowsColumns.class, null, (TermIdent) t);
              return property == GridTemplateRowsColumns.AUTO
                      || property == GridTemplateRowsColumns.MIN_CONTENT
                      || property == GridTemplateRowsColumns.MAX_CONTENT;
          }
          return false;
      }
docs: <track-breadth> = <length> | <percentage> | <flex> | min-content |
  max-content | auto