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

Source/core/paint/BoxClipper.cpp

Index: Source/core/paint/BoxClipper.cpp
diff --git a/Source/core/paint/BoxClipper.cpp b/Source/core/paint/BoxClipper.cpp
index ce1de5652c9232df953bec572020b00fd471b139..28bc41222d34058a6f607677d24e23ad83fece89 100644
--- a/Source/core/paint/BoxClipper.cpp
+++ b/Source/core/paint/BoxClipper.cpp
@@ -55,16 +55,16 @@ BoxClipper::BoxClipper(LayoutBox& box, const PaintInfo& paintInfo, const LayoutP
     if (RuntimeEnabledFeatures::slimmingPaintEnabled())
         m_clipType = m_paintInfo.displayItemTypeForClipping();
 
-    OwnPtr<ClipDisplayItem> clipDisplayItem = ClipDisplayItem::create(m_box, m_clipType, pixelSnappedIntRect(clipRect));
+    ClipDisplayItem clipDisplayItem(m_box, m_clipType, pixelSnappedIntRect(clipRect));
     if (hasBorderRadius)
-        clipDisplayItem->roundedRectClips().append(clipRoundedRect);
+        clipDisplayItem.roundedRectClips().append(clipRoundedRect);
 
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         ASSERT(m_paintInfo.context->displayItemList());
         if (!m_paintInfo.context->displayItemList()->displayItemConstructionIsDisabled())
-            m_paintInfo.context->displayItemList()->add(clipDisplayItem.release());
+            m_paintInfo.context->displayItemList()->add(clipDisplayItem);
     } else {
-        clipDisplayItem->replay(*paintInfo.context);
+        clipDisplayItem.replay(*paintInfo.context);
     }
 
     m_pushedClip = true;
@@ -78,14 +78,13 @@ BoxClipper::~BoxClipper()
     ASSERT(m_box.hasControlClip() || (m_box.hasOverflowClip() && !m_box.layer()->isSelfPaintingLayer()));
 
     DisplayItem::Type endType = DisplayItem::clipTypeToEndClipType(m_clipType);
+    EndClipDisplayItem endClipDisplayItem(m_box, endType);
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         if (m_paintInfo.context->displayItemList()->displayItemConstructionIsDisabled())
             return;
-        OwnPtr<EndClipDisplayItem> endClipDisplayItem = EndClipDisplayItem::create(m_box, endType);
         ASSERT(m_paintInfo.context->displayItemList());
-        m_paintInfo.context->displayItemList()->add(endClipDisplayItem.release());
+        m_paintInfo.context->displayItemList()->add(endClipDisplayItem);
     } else {
-        EndClipDisplayItem endClipDisplayItem(m_box, endType);
         endClipDisplayItem.replay(*m_paintInfo.context);
     }
 }