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

Source/core/paint/ScrollRecorder.cpp

Index: Source/core/paint/ScrollRecorder.cpp
diff --git a/Source/core/paint/ScrollRecorder.cpp b/Source/core/paint/ScrollRecorder.cpp
index bbc320b683e32d46d749edacfadbc2ce4a72fa05..dafae0de4a82d61165114b72debef118887544a1 100644
--- a/Source/core/paint/ScrollRecorder.cpp
+++ b/Source/core/paint/ScrollRecorder.cpp
@@ -17,13 +17,13 @@ ScrollRecorder::ScrollRecorder(GraphicsContext& context, const DisplayItemClient
     , m_beginItemType(DisplayItem::paintPhaseToScrollType(phase))
     , m_context(context)
 {
+    BeginScrollDisplayItem scrollDisplayItem(m_client, m_beginItemType, currentOffset);
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         ASSERT(m_context.displayItemList());
         if (m_context.displayItemList()->displayItemConstructionIsDisabled())
             return;
-        m_context.displayItemList()->add(BeginScrollDisplayItem::create(m_client, m_beginItemType, currentOffset));
+        m_context.displayItemList()->add(scrollDisplayItem);
     } else {
-        BeginScrollDisplayItem scrollDisplayItem(m_client, m_beginItemType, currentOffset);
         scrollDisplayItem.replay(m_context);
     }
 }
@@ -31,13 +31,13 @@ ScrollRecorder::ScrollRecorder(GraphicsContext& context, const DisplayItemClient
 ScrollRecorder::~ScrollRecorder()
 {
     DisplayItem::Type endItemType = DisplayItem::scrollTypeToEndScrollType(m_beginItemType);
+    EndScrollDisplayItem endScrollDisplayItem(m_client, endItemType);
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         ASSERT(m_context.displayItemList());
         if (m_context.displayItemList()->displayItemConstructionIsDisabled())
             return;
-        m_context.displayItemList()->add(EndScrollDisplayItem::create(m_client, endItemType));
+        m_context.displayItemList()->add(endScrollDisplayItem);
     } else {
-        EndScrollDisplayItem endScrollDisplayItem(m_client, endItemType);
         endScrollDisplayItem.replay(m_context);
     }
 }