Track safe nodes for DDFS removal during GC/rr_tags.
Track safe nodes for DDFS removal during GC/rr_tags.

pooya/disco,mozilla/disco,beni55/disco,beni55/disco,scrapinghub/disco,scrapinghub/disco,pombredanne/disco,oldmantaiter/disco,pavlobaron/disco_playground,pombredanne/disco,seabirdzh/disco,mwilliams3/disco,pombredanne/disco,beni55/disco,discoproject/disco,ErikDubbelboer/disco,mozilla/disco,simudream/disco,mwilliams3/disco,discoproject/disco,scrapinghub/disco,simudream/disco,pavlobaron/disco_playground,oldmantaiter/disco,pombredanne/disco,ErikDubbelboer/disco,discoproject/disco,seabirdzh/disco,pooya/disco,ktkt2009/disco,ktkt2009/disco,ErikDubbelboer/disco,mwilliams3/disco,beni55/disco,simudream/disco,ErikDubbelboer/disco,discoproject/disco,ktkt2009/disco,seabirdzh/disco,discoproject/disco,ktkt2009/disco,oldmantaiter/disco,pooya/disco,oldmantaiter/disco,mozilla/disco,mwilliams3/disco,mwilliams3/disco,seabirdzh/disco,mozilla/disco,oldmantaiter/disco,beni55/disco,pombredanne/disco,seabirdzh/disco,pooya/disco,simudream/disco,ErikDubbelboer/disco,pavlobaron/disco_playground,scrapinghub/disco,pavlobaron/disco_playground,simudream/disco,ktkt2009/disco