Separate display item clients for negative and normal/positive z-order children

third_party/WebKit/Source/core/paint/PaintLayer.h

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 4b47a60f6b8c037eafdd3e9489a0d3542a69666c..dc9963b09e710c7ef21590eab4c3be6886d3c3d5 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -616,8 +616,11 @@ public:
     IntSize previousScrollOffsetAccumulationForPainting() const { return m_previousScrollOffsetAccumulationForPainting; }
     void setPreviousScrollOffsetAccumulationForPainting(const IntSize& s) { m_previousScrollOffsetAccumulationForPainting = s; }
 
-    // For subsequence display items.
-    DisplayItemClient displayItemClient() const { return toDisplayItemClient(this); }
+    DisplayItemClientWrapper displayItemClientForNegativeZOrderChildren() const;
+    DisplayItemClientWrapper displayItemClientForNormalAndPositiveZOrderChildren() const;
+
+    static String debugNameForNegativeZOrderChildrenDisplayItemClient(const PaintLayer& layer) { return layer.debugName() + " negative z-order children"; }
+    static String debugNameForNormalAndPositiveZOrderChildrenDisplayItemClient(const PaintLayer& layer) { return layer.debugName() + " normal and positive z-order children"; }
 
 private:
     // Bounding box in the coordinates of this layer.