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

Source/platform/graphics/paint/DrawingDisplayItem.cpp

Index: Source/platform/graphics/paint/DrawingDisplayItem.cpp
diff --git a/Source/platform/graphics/paint/DrawingDisplayItem.cpp b/Source/platform/graphics/paint/DrawingDisplayItem.cpp
index 0c75954da7a014ffb5b883a11726c1269459bf8e..bd36ac2572cd63667533432868a53112b973baab 100644
--- a/Source/platform/graphics/paint/DrawingDisplayItem.cpp
+++ b/Source/platform/graphics/paint/DrawingDisplayItem.cpp
@@ -6,6 +6,7 @@
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 
 #include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/paint/DisplayItems.h"
 #include "public/platform/WebDisplayItemList.h"
 
 namespace blink {
@@ -22,6 +23,13 @@ void DrawingDisplayItem::appendToWebDisplayItemList(WebDisplayItemList* list) co
         list->appendDrawingItem(m_picture.get());
 }
 
+void DrawingDisplayItem::appendByMoving(DisplayItems& destination)
+{
+    destination.emplaceBack<DrawingDisplayItem>(
+        DisplayItemClientWrapperHelper(*this),
+        type(), m_picture.release());
+}
+
 bool DrawingDisplayItem::drawsContent() const
 {
     return m_picture;