StructTraits optimizations

cc/ipc/returned_resource_struct_traits.h

Index: cc/ipc/returned_resource_struct_traits.h
diff --git a/cc/ipc/returned_resource_struct_traits.h b/cc/ipc/returned_resource_struct_traits.h
index 38e02fda9c5323659544ffe55954700683395bbd..1f9ff55005ca623ed7853c01fab8ab9a98c3bfe8 100644
--- a/cc/ipc/returned_resource_struct_traits.h
+++ b/cc/ipc/returned_resource_struct_traits.h
@@ -16,7 +16,8 @@ struct StructTraits<cc::mojom::ReturnedResource, cc::ReturnedResource> {
     return resource.id;
   }
 
-  static gpu::SyncToken sync_token(const cc::ReturnedResource& resource) {
+  static const gpu::SyncToken& sync_token(
+      const cc::ReturnedResource& resource) {
     return resource.sync_token;
   }