Add SurfaceReference class.

cc/ipc/local_frame_id_struct_traits.h

Index: cc/ipc/local_frame_id_struct_traits.h
diff --git a/cc/ipc/local_frame_id_struct_traits.h b/cc/ipc/local_frame_id_struct_traits.h
index 514bd4cbeaeb11dd7602dd77d60b2f5deddf41e9..4dd01d6fba44f52fcfdcc4bfe9d9608f397c9fce 100644
--- a/cc/ipc/local_frame_id_struct_traits.h
+++ b/cc/ipc/local_frame_id_struct_traits.h
@@ -24,12 +24,8 @@ struct StructTraits<cc::mojom::LocalFrameIdDataView, cc::LocalFrameId> {
 
   static bool Read(cc::mojom::LocalFrameIdDataView data,
                    cc::LocalFrameId* out) {
-    base::UnguessableToken nonce;
-    if (!data.ReadNonce(&nonce))
-      return false;
-
-    *out = cc::LocalFrameId(data.local_id(), nonce);
-    return true;
+    out->local_id_ = data.local_id();
+    return data.ReadNonce(&out->nonce_);
   }
 };