Clean up BoxClipper

Source/core/paint/BoxClipper.h

Index: Source/core/paint/BoxClipper.h
diff --git a/Source/core/paint/BoxClipper.h b/Source/core/paint/BoxClipper.h
index 106bfec7ee8fb5332cb2bb91f579d73ad7906e08..59b6a6dd93c9b707cb91cba87286d2f21e596952 100644
--- a/Source/core/paint/BoxClipper.h
+++ b/Source/core/paint/BoxClipper.h
@@ -17,15 +17,11 @@ enum ContentsClipBehavior { ForceContentsClip, SkipContentsClipIfPossible };
 
 class BoxClipper {
 public:
-    BoxClipper(LayoutBox&, const PaintInfo&, const LayoutPoint& accumulatedOffset, ContentsClipBehavior);
+    BoxClipper(const LayoutBox&, const PaintInfo&, const LayoutPoint& accumulatedOffset, ContentsClipBehavior);
     ~BoxClipper();
-
-    bool pushedClip() { return m_pushedClip; }
 private:
-    bool m_pushedClip;
-    LayoutPoint m_accumulatedOffset;
+    const LayoutBox& m_box;
     const PaintInfo& m_paintInfo;
-    LayoutBox& m_box;
     DisplayItem::Type m_clipType;
 };