Large canvas does not honor containing div's border radius

Source/core/platform/graphics/GraphicsLayer.h

Index: Source/core/platform/graphics/GraphicsLayer.h
diff --git a/Source/core/platform/graphics/GraphicsLayer.h b/Source/core/platform/graphics/GraphicsLayer.h
index 72206c30f2d891931431cb3a92570a1b100f3cc1..72753290fabfdca1889cd09791924c5466044ae9 100644
--- a/Source/core/platform/graphics/GraphicsLayer.h
+++ b/Source/core/platform/graphics/GraphicsLayer.h
@@ -250,6 +250,9 @@ public:
 
     GraphicsLayer* maskLayer() const { return m_maskLayer; }
     void setMaskLayer(GraphicsLayer*);
+
+    GraphicsLayer* borderRadiusLayer() const { return m_borderRadiusLayer; }
+    void setBorderRadiusLayer(GraphicsLayer*);
     
     // The given layer will replicate this layer and its children; the replica renders behind this layer.
     void setReplicatedByLayer(GraphicsLayer*);
@@ -533,6 +536,7 @@ protected:
     GraphicsLayer* m_parent;
 
     GraphicsLayer* m_maskLayer; // Reference to mask layer. We don't own this.
+    GraphicsLayer* m_borderRadiusLayer; // Reference to border radius mask layer. We don't own this.
 
     GraphicsLayer* m_replicaLayer; // A layer that replicates this layer. We only allow one, for now.
                                    // The replica is not parented; this is the primary reference to it.