Save previous paint offset in LayoutObject

Source/core/paint/LineBoxListPainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef LineBoxListPainter_h
 #define LineBoxListPainter_h
 
 #include "core/style/ComputedStyleConstants.h"
 #include "wtf/Allocator.h"
 
 namespace blink {
 
 class LayoutPoint;
 struct PaintInfo;
 class LayoutBoxModelObject;
 class LineBoxList;
 
 class LineBoxListPainter {
     STACK_ALLOCATED();
 public:
     LineBoxListPainter(LineBoxList& lineBoxList) : m_lineBoxList(lineBoxList) { }
 
     void paint(LayoutBoxModelObject*, const PaintInfo&, const LayoutPoint&) const;
 
+    void invalidateLineBoxPaintOffsets(const PaintInfo&) const;
+
 private:
     LineBoxList& m_lineBoxList;
 };
 
 } // namespace blink
 
 #endif // LineBoxListPainter_h