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

Source/platform/graphics/paint/ClipDisplayItem.cpp

Index: Source/platform/graphics/paint/ClipDisplayItem.cpp
diff --git a/Source/platform/graphics/paint/ClipDisplayItem.cpp b/Source/platform/graphics/paint/ClipDisplayItem.cpp
index 26eb7900ec54c0b23c77b90f5e579c9607c4df57..fbd7d35e526a6b6753a2da987bec4e2dec6b8310 100644
--- a/Source/platform/graphics/paint/ClipDisplayItem.cpp
+++ b/Source/platform/graphics/paint/ClipDisplayItem.cpp
@@ -7,6 +7,7 @@
 
 #include "platform/geometry/FloatRoundedRect.h"
 #include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/paint/DisplayItems.h"
 #include "public/platform/WebDisplayItemList.h"
 #include "third_party/skia/include/core/SkScalar.h"
 
@@ -42,6 +43,14 @@ void ClipDisplayItem::appendToWebDisplayItemList(WebDisplayItemList* list) const
     list->appendClipItem(m_clipRect, webRoundedRects);
 }
 
+void ClipDisplayItem::appendByMoving(DisplayItems& destination)
+{
+    ClipDisplayItem& displayItem = destination.emplaceBack<ClipDisplayItem>(
+        DisplayItemClientWrapperHelper(*this),
+        type(), m_clipRect, m_operation);
+    displayItem.roundedRectClips().swap(roundedRectClips());
+}
+
 void EndClipDisplayItem::replay(GraphicsContext& context)
 {
     context.restore();
@@ -52,6 +61,12 @@ void EndClipDisplayItem::appendToWebDisplayItemList(WebDisplayItemList* list) co
     list->appendEndClipItem();
 }
 
+void EndClipDisplayItem::appendByMoving(DisplayItems& destination)
+{
+    destination.emplaceBack<EndClipDisplayItem>(
+        DisplayItemClientWrapperHelper(*this), type());
+}
+
 #ifndef NDEBUG
 void ClipDisplayItem::dumpPropertiesAsDebugString(WTF::StringBuilder& stringBuilder) const
 {