Zygote : Block SIGCHLD during fork. am: ba4ee699 am: 649225a5 am: b1ef9414 -s ours am: 53ad3493 am: 19689714 am: 22c3317e am: 646a6e0a am: 1656e136 am: 06f9faa9 am: 9aa560c2 Change-Id: Icde48b3b9951a7e2be24ba745d58e644fae5b095