Fix severely broken dirty descendents optimization.
Fix severely broken dirty descendents optimization.

mozilla/shumway,yurydelendik/shumway,yurydelendik/shumway,yurydelendik/shumway,yurydelendik/shumway,mozilla/shumway,yurydelendik/shumway,yurydelendik/shumway,yurydelendik/shumway,mozilla/shumway,mozilla/shumway,mozilla/shumway,yurydelendik/shumway,mozilla/shumway,mozilla/shumway,mozilla/shumway