Add comment to the buffer_state_bit_.

Test: None
Bug: 112007999
Change-Id: Ibc01cc879e638af9712495317260aabcb515781d
diff --git a/libs/vr/libbufferhub/include/private/dvr/buffer_hub_base.h b/libs/vr/libbufferhub/include/private/dvr/buffer_hub_base.h
index b75fd61..24db241 100644
--- a/libs/vr/libbufferhub/include/private/dvr/buffer_hub_base.h
+++ b/libs/vr/libbufferhub/include/private/dvr/buffer_hub_base.h
@@ -155,7 +155,12 @@
   // for logging and debugging purposes only and should not be used for lookup
   // or any other functional purpose as a security precaution.
   int id_;
+
+  // Channel id.
   int cid_;
+
+  // Client bit mask which indicates the locations of this client object in the
+  // buffer_state_.
   uint64_t buffer_state_bit_{0ULL};
   IonBuffer buffer_;
   IonBuffer metadata_buffer_;