Merge "Adding per-method clang thread safety annotations"

#define PT_GUARDED_BY(x) \

      THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))

#define EXCLUSIVE_LOCKS_REQUIRED(...) \

      THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(__VA_ARGS__))

#define SHARED_LOCKS_REQUIRED(...) \

      THREAD_ANNOTATION_ATTRIBUTE__(shared_locks_required(__VA_ARGS__))

#define ACQUIRED_BEFORE(...) \

      THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(__VA_ARGS__))