Slimming Paint phase 2 compositing algorithm plumbing

Source/platform/graphics/paint/DisplayItemList.cpp

Index: Source/platform/graphics/paint/DisplayItemList.cpp
diff --git a/Source/platform/graphics/paint/DisplayItemList.cpp b/Source/platform/graphics/paint/DisplayItemList.cpp
index 9b332ae4f9d71d4bbf6304cc82c2274a718be989..c0775acd10df6eec40ca833558fd46737dc58ad4 100644
--- a/Source/platform/graphics/paint/DisplayItemList.cpp
+++ b/Source/platform/graphics/paint/DisplayItemList.cpp
@@ -209,7 +209,9 @@ DisplayItems::iterator DisplayItemList::findOutOfOrderCachedItemForward(DisplayI
 // The algorithm is O(|m_currentDisplayItems| + |m_newDisplayItems|).
 // Coefficients are related to the ratio of out-of-order [Subtree]CachedDisplayItems
 // and the average number of (Drawing|BeginSubtree)DisplayItems per client.
-void DisplayItemList::commitNewDisplayItems()
+//
+// TODO: Implement the DisplayListDiff algorithm for SlimmingPaintV2.
+void DisplayItemList::commitNewDisplayItems(DisplayListDiff*)
 {
     TRACE_EVENT2("blink,benchmark", "DisplayItemList::commitNewDisplayItems", "current_display_list_size", (int)m_currentDisplayItems.size(),
         "num_non_cached_new_items", (int)m_newDisplayItems.size() - m_numCachedItems);