Merge "Add read-write lock for per-user operations." am: 18e8bbb4d0 am: b00e5af674 am: beaca83f00 am: 6c2a2967df

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/1901110

Change-Id: If2479ea7b33a95cf2e73a8519c8411ee95a885f9