diff --git a/gfx/layers/LayerTreeInvalidation.cpp b/gfx/layers/LayerTreeInvalidation.cpp
index 567171a9766c..92df53404fb2 100644
--- a/gfx/layers/LayerTreeInvalidation.cpp
+++ b/gfx/layers/LayerTreeInvalidation.cpp
@@ -69,14 +69,6 @@ AddRegion(nsIntRegion& aDest, const nsIntRegion& aSource)
   aDest.SimplifyOutward(20);
 }
 
-
-static nsIntRegion
-TransformRegion(nsIntRegion& aRegion, const gfx3DMatrix& aTransform)
-{
-  aRegion.Transform(aTransform);
-  return aRegion;
-}
-
 /**
  * Walks over this layer, and all descendant layers.
  * If any of these are a ContainerLayer that reports invalidations to a PresShell,
@@ -325,7 +317,8 @@ struct ContainerLayerProperties : public LayerPropertiesBase
 
     gfx3DMatrix transform;
     gfx::To3DMatrix(mLayer->GetTransform(), transform);
-    return TransformRegion(result, transform);
+    result.Transform(transform);
+    return result;
   }
 
   // The old list of children: