Revert "Reworks the clipping logic" and follow-up.

Source/core/layout/ClipRects.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 13 matching lines @@
  */
 
 #ifndef ClipRects_h
 #define ClipRects_h
 
 #include "core/layout/ClipRect.h"
 #include "wtf/RefCounted.h"
 
 namespace blink {
 
-class DeprecatedPaintLayer;
-
-class ClipRects {
+class ClipRects : public RefCounted<ClipRects> {
     WTF_MAKE_FAST_ALLOCATED(ClipRects);
 public:
+    static PassRefPtr<ClipRects> create()
+    {
+        return adoptRef(new ClipRects);
+    }
+    static PassRefPtr<ClipRects> create(const ClipRects& other)
+    {
+        return adoptRef(new ClipRects(other));
+    }
 
     ClipRects()
-        : m_rootLayer(nullptr)
-        , m_fixed(0)
+        : m_fixed(0)
     {
     }
 
     void reset(const LayoutRect& r)
     {
         m_overflowClipRect = r;
         m_fixedClipRect = r;
         m_posClipRect = r;
         m_fixed = 0;
     }
@@ skipping 17 matching lines @@
             && m_posClipRect == other.posClipRect()
             && fixed() == other.fixed();
     }
 
     ClipRects& operator=(const ClipRects& other)
     {
         m_overflowClipRect = other.overflowClipRect();
         m_fixedClipRect = other.fixedClipRect();
         m_posClipRect = other.posClipRect();
         m_fixed = other.fixed();
-        m_rootLayer = other.m_rootLayer;
         return *this;
     }
 
-    void setRootLayer(const DeprecatedPaintLayer* layer)
-    {
-        m_rootLayer = layer;
-    }
-
-    const DeprecatedPaintLayer* rootLayer()
-    {
-        return m_rootLayer;
-    }
-
 private:
     ClipRects(const LayoutRect& r)
-        : m_rootLayer(nullptr)
-        , m_overflowClipRect(r)
+        : m_overflowClipRect(r)
         , m_fixedClipRect(r)
         , m_posClipRect(r)
         , m_fixed(0)
     {
     }
 
     ClipRects(const ClipRects& other)
-        : m_rootLayer(other.m_rootLayer)
-        , m_overflowClipRect(other.overflowClipRect())
+        : m_overflowClipRect(other.overflowClipRect())
         , m_fixedClipRect(other.fixedClipRect())
         , m_posClipRect(other.posClipRect())
         , m_fixed(other.fixed())
     {
     }
 
-    // ClipRects are accumulated relative to this layer. Its clips and the clips
-    // of its descendents are intersected down to the layer being calculated. It
-    // also determines the coordinate space of the clips.
-    const DeprecatedPaintLayer* m_rootLayer;
     ClipRect m_overflowClipRect;
     ClipRect m_fixedClipRect;
     ClipRect m_posClipRect;
     unsigned m_fixed;
 };
 
 } // namespace blink
 
 #endif // ClipRects_h