WIP for display item list backed by ListContainer

Source/platform/graphics/paint/ScrollDisplayItem.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 ScrollDisplayItem_h
 #define ScrollDisplayItem_h
 
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class PLATFORM_EXPORT BeginScrollDisplayItem : public PairedBeginDisplayItem {
-    WTF_MAKE_FAST_ALLOCATED(BeginScrollDisplayItem);
 public:
-    static PassOwnPtr<BeginScrollDisplayItem> create(const DisplayItemClientWrapper& client, Type type, const IntSize& currentOffset)
+    void setNew(IntSize& currentOffset)
     {
-        return adoptPtr(new BeginScrollDisplayItem(client, type, currentOffset));
-    }
-
-    BeginScrollDisplayItem(const DisplayItemClientWrapper& client, Type type, const IntSize& currentOffset)
-        : PairedBeginDisplayItem(client, type)
-        , m_currentOffset(currentOffset)
-    {
-        ASSERT(isScrollType(type));
+        m_currentOffset = currentOffset;
+        ASSERT(isScrollType(type()));
     }
 
     virtual void replay(GraphicsContext&) override;
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override;
 
 private:
 #ifndef NDEBUG
     virtual void dumpPropertiesAsDebugString(WTF::StringBuilder&) const override final;
 #endif
 
-    const IntSize m_currentOffset;
+    IntSize m_currentOffset;
 };
 
 class PLATFORM_EXPORT EndScrollDisplayItem : public PairedEndDisplayItem {
-    WTF_MAKE_FAST_ALLOCATED(EndScrollDisplayItem);
 public:
-    static PassOwnPtr<EndScrollDisplayItem> create(const DisplayItemClientWrapper& client, Type type)
-    {
-        return adoptPtr(new EndScrollDisplayItem(client, type));
-    }
-
-    EndScrollDisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : PairedEndDisplayItem(client, type)
-    {
-        ASSERT(isEndScrollType(type));
-    }
-
     virtual void replay(GraphicsContext&) override;
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override;
 
 private:
 #if ENABLE(ASSERT)
     virtual bool isEndAndPairedWith(DisplayItem::Type otherType) const override final { return DisplayItem::isScrollType(otherType); }
 #endif
 };
 
 } // namespace blink
 
 #endif // ScrollDisplayItem_h