Zygote : Block SIGCHLD during fork. am: ba4ee699 am: 649225a5 am: b1ef9414 -s ours am: 53ad3493 am: 19689714 am: 22c3317e am: 646a6e0a Change-Id: Ib37e1cb996b5ecf06c86ad89ea38503b5a82af9c