[Slimming Paint] Blink-side contiguous allocation of display items.

Source/platform/graphics/paint/CachedDisplayItem.h

Index: Source/platform/graphics/paint/CachedDisplayItem.h
diff --git a/Source/platform/graphics/paint/CachedDisplayItem.h b/Source/platform/graphics/paint/CachedDisplayItem.h
index ac8390102cd2f1e6eacc1007e26010a710890b36..d8c612f0240bcd7d1c335d3b91ad89ab0065ddeb 100644
--- a/Source/platform/graphics/paint/CachedDisplayItem.h
+++ b/Source/platform/graphics/paint/CachedDisplayItem.h
@@ -21,16 +21,18 @@ public:
         return adoptPtr(new CachedDisplayItem(client, type));
     }
 
-private:
     CachedDisplayItem(const DisplayItemClientWrapper& client, Type type)
         : DisplayItem(client, type)
     {
         ASSERT(isCachedType(type));
     }
 
+private:
     // CachedDisplayItem is never replayed or appended to WebDisplayItemList.
     virtual void replay(GraphicsContext&) override final { ASSERT_NOT_REACHED(); }
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override final { ASSERT_NOT_REACHED(); }
+
+    virtual void appendByMoving(DisplayItems&) override;
 };
 
 } // namespace blink