WIP for display item list backed by ListContainer

Source/platform/graphics/paint/SubtreeDisplayItem.h

Index: Source/platform/graphics/paint/SubtreeDisplayItem.h
diff --git a/Source/platform/graphics/paint/SubtreeDisplayItem.h b/Source/platform/graphics/paint/SubtreeDisplayItem.h
index efddb5edab88a954e084b6139d750d0964461f53..a70328d121e9f57cde01965dcf9146c545040605 100644
--- a/Source/platform/graphics/paint/SubtreeDisplayItem.h
+++ b/Source/platform/graphics/paint/SubtreeDisplayItem.h
@@ -12,55 +12,14 @@
 namespace blink {
 
 class PLATFORM_EXPORT SubtreeCachedDisplayItem : public DisplayItem {
-    WTF_MAKE_FAST_ALLOCATED(SubtreeCachedDisplayItem);
-public:
-    static PassOwnPtr<SubtreeCachedDisplayItem> create(const DisplayItemClientWrapper& client, Type type)
-    {
-        return adoptPtr(new SubtreeCachedDisplayItem(client, type));
-    }
-
-private:
-    SubtreeCachedDisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : DisplayItem(client, type)
-    {
-        ASSERT(isSubtreeCachedType(type));
-    }
-
     virtual void replay(GraphicsContext&) override final { ASSERT_NOT_REACHED(); }
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override final { ASSERT_NOT_REACHED(); }
 };
 
 class PLATFORM_EXPORT BeginSubtreeDisplayItem : public PairedBeginDisplayItem {
-    WTF_MAKE_FAST_ALLOCATED(BeginSubtreeDisplayItem);
-public:
-    static PassOwnPtr<BeginSubtreeDisplayItem> create(const DisplayItemClientWrapper& client, Type type)
-    {
-        return adoptPtr(new BeginSubtreeDisplayItem(client, type));
-    }
-
-private:
-    BeginSubtreeDisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : PairedBeginDisplayItem(client, type)
-    {
-        ASSERT(isBeginSubtreeType(type));
-    }
 };
 
 class PLATFORM_EXPORT EndSubtreeDisplayItem : public PairedEndDisplayItem {
-    WTF_MAKE_FAST_ALLOCATED(EndSubtreeDisplayItem);
-public:
-    static PassOwnPtr<EndSubtreeDisplayItem> create(const DisplayItemClientWrapper& client, Type type)
-    {
-        return adoptPtr(new EndSubtreeDisplayItem(client, type));
-    }
-
-private:
-    EndSubtreeDisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : PairedEndDisplayItem(client, type)
-    {
-        ASSERT(isEndSubtreeType(type));
-    }
-
 #if ENABLE(ASSERT)
     virtual bool isEndAndPairedWith(DisplayItem::Type otherType) const override final { return DisplayItem::isBeginSubtreeType(otherType); }
 #endif