Remove stale TODO about calling elementAt

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 2947afd84b91892ae388df0b67a981c1e7c63d68..9c8fad763e60b0b3cbb4dbcea05602878a2bd54c 100644
--- a/Source/platform/graphics/paint/DisplayItemList.cpp
+++ b/Source/platform/graphics/paint/DisplayItemList.cpp
@@ -147,7 +147,6 @@ size_t DisplayItemList::findMatchingItemFromIndex(const DisplayItem::Id& id, con
 
     const Vector<size_t>& indices = it->value;
     for (size_t index : indices) {
-        // TODO(pdr): elementAt is not cheap so this should be refactored (See crbug.com/505965).
         const DisplayItem& existingItem = list[index];
         ASSERT(!existingItem.isValid() || existingItem.client() == id.client);
         if (existingItem.isValid() && id.matches(existingItem))