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: 56b7e56890  -s ours

Change-Id: Ie6e9e39c63d9340de659ae428ee5bf79148aa95c