Let DeprecatedPaintLayer be client of subsequence display items

Source/core/paint/DeprecatedPaintLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 533 matching lines @@
         RootOfTransparencyClipBox
     };
 
     static LayoutRect transparencyClipBox(const DeprecatedPaintLayer*, const DeprecatedPaintLayer* rootLayer, TransparencyClipBoxBehavior transparencyBehavior,
         TransparencyClipBoxMode transparencyMode, GlobalPaintFlags = GlobalPaintNormalPhase);
 
     bool needsRepaint() const { return m_needsRepaint; }
     void setNeedsRepaint();
     void clearNeedsRepaint() { m_needsRepaint = false; }
 
+    // For subsequence display items.
+    DisplayItemClient displayItemClient() const { return toDisplayItemClient(this); }
+
 private:
     // Bounding box in the coordinates of this layer.
     LayoutRect logicalBoundingBox() const;
 
     bool hasOverflowControls() const;
 
     void dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 
     // Returns true if the position changed.
     bool updateLayerPosition();
@@ skipping 173 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::DeprecatedPaintLayer*);
 void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif // Layer_h