Merge "SurfaceFlinger: add more thread-safety annotations." into udc-dev am: b82f5ddf

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/native/+/22344060



Change-Id: I85e12865e233181dac6957f7923e965857575d6a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>