Blink-side contiguous allocation of display items.

Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp

Index: Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
diff --git a/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp b/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
index 7704bcef04dc2545772e881fc0ebb1e7ddc8889c..1238cb5637435604dadb922286da16fd5ab1fe9c 100644
--- a/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
+++ b/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
@@ -2128,24 +2128,24 @@ void CompositedDeprecatedPaintLayerMapping::doPaintTask(const GraphicsLayerPaint
         // FIXME: Combine similar code here and LayerClipRecorder.
         dirtyRect.intersect(paintInfo.localClipRectForSquashedLayer);
         {
-            OwnPtr<DisplayItem> clipDisplayItem = ClipDisplayItem::create(*this, DisplayItem::ClipLayerOverflowControls, dirtyRect);
             if (context->displayItemList()) {
                 ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
                 if (!context->displayItemList()->displayItemConstructionIsDisabled())
-                    context->displayItemList()->add(clipDisplayItem.release());
+                    context->displayItemList()->createAndAppendIfNeeded<ClipDisplayItem>(*this, DisplayItem::ClipLayerOverflowControls, dirtyRect);
             } else {
-                clipDisplayItem->replay(*context);
+                ClipDisplayItem clipDisplayItem(*this, DisplayItem::ClipLayerOverflowControls, dirtyRect);
+                clipDisplayItem.replay(*context);
             }
         }
         DeprecatedPaintLayerPainter(*paintInfo.paintLayer).paintLayer(context, paintingInfo, paintLayerFlags);
         {
-            OwnPtr<DisplayItem> endClipDisplayItem = EndClipDisplayItem::create(*this, DisplayItem::clipTypeToEndClipType(DisplayItem::ClipLayerOverflowControls));
             if (context->displayItemList()) {
                 ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
                 if (!context->displayItemList()->displayItemConstructionIsDisabled())
-                    context->displayItemList()->add(endClipDisplayItem.release());
+                    context->displayItemList()->createAndAppendIfNeeded<EndClipDisplayItem>(*this, DisplayItem::clipTypeToEndClipType(DisplayItem::ClipLayerOverflowControls));
             } else {
-                endClipDisplayItem->replay(*context);
+                EndClipDisplayItem endClipDisplayItem(*this, DisplayItem::clipTypeToEndClipType(DisplayItem::ClipLayerOverflowControls));
+                endClipDisplayItem.replay(*context);
             }
         }
     }