DO NOT MERGE ANYWHERE: [AsyncChannel] Fix race in handling of sync result am: 02d802e71e  -s ours am: b5ee561702  -s ours am: 7391bedf87  -s ours am: 8597268bc2  -s ours
am: 8f33b0bd96  -s ours

Change-Id: Icd6c2ff79f3d697cf308ca4e94d0e6fb0ce9dff4