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..8daea107206eabf3009f0bbaca8a4c5e80eb846c 100644
--- a/cc/ipc/local_frame_id_struct_traits.h
+++ b/cc/ipc/local_frame_id_struct_traits.h
@@ -24,11 +24,9 @@ struct StructTraits<cc::mojom::LocalFrameIdDataView, cc::LocalFrameId> {
 
   static bool Read(cc::mojom::LocalFrameIdDataView data,
                    cc::LocalFrameId* out) {
-    base::UnguessableToken nonce;
-    if (!data.ReadNonce(&nonce))
+    out->local_id_ = data.local_id();
+    if (!data.ReadNonce(&out->nonce_))

[Tom Sepez, 2016/11/30 18:35:05]

nit: or just
  return data.ReadNonce(&out->nonce_);

[kylechar, 2016/11/30 22:44:58]

Done.

       return false;
-
-    *out = cc::LocalFrameId(data.local_id(), nonce);
     return true;
   }
 };