SurfaceFlinger: fix a potential race condition in stealReceiveChannel am:...

SurfaceFlinger: fix a potential race condition in stealReceiveChannel am: 899e8cd0 am: 2afe6245 am: b99ea55f am: 8721fc2d

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/native/+/18764134



Change-Id: I63f4ae9eb2479b590cf020934a6c70dd82e5059f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>