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

Source/core/paint/SubtreeRecorder.cpp

Index: Source/core/paint/SubtreeRecorder.cpp
diff --git a/Source/core/paint/SubtreeRecorder.cpp b/Source/core/paint/SubtreeRecorder.cpp
index 7597f1b9429cf7b3ac061c0c1887019658615e58..383b3bb0c4f42c9bb81b48abdeca06757e247152 100644
--- a/Source/core/paint/SubtreeRecorder.cpp
+++ b/Source/core/paint/SubtreeRecorder.cpp
@@ -30,8 +30,10 @@ SubtreeRecorder::~SubtreeRecorder()
     if (!RuntimeEnabledFeatures::slimmingPaintEnabled())
         return;
 
-    if (m_begun)
-        m_displayItemList->add(EndSubtreeDisplayItem::create(m_subtreeRoot, DisplayItem::paintPhaseToEndSubtreeType(m_paintPhase)));
+    if (m_begun) {
+        EndSubtreeDisplayItem endSubtree(m_subtreeRoot, DisplayItem::paintPhaseToEndSubtreeType(m_paintPhase));
+        m_displayItemList->add(endSubtree);
+    }
 }
 
 void SubtreeRecorder::begin()
@@ -40,7 +42,8 @@ void SubtreeRecorder::begin()
         return;
     if (m_displayItemList->displayItemConstructionIsDisabled())
         return;
-    m_displayItemList->add(BeginSubtreeDisplayItem::create(m_subtreeRoot, DisplayItem::paintPhaseToBeginSubtreeType(m_paintPhase)));
+    BeginSubtreeDisplayItem beginSubtree(m_subtreeRoot, DisplayItem::paintPhaseToBeginSubtreeType(m_paintPhase));
+    m_displayItemList->add(beginSubtree);
     m_begun = true;
 }