cc: Implement RemoveLast for DisplayItemList.

cc/playback/display_item_list.cc

Index: cc/playback/display_item_list.cc
diff --git a/cc/playback/display_item_list.cc b/cc/playback/display_item_list.cc
index 5ee754ba7605a8b96bd9dd72f266a7b05940ea72..66c4ecd277be775da2b5be4051f0c6c32eb0a89c 100644
--- a/cc/playback/display_item_list.cc
+++ b/cc/playback/display_item_list.cc
@@ -159,6 +159,15 @@ void DisplayItemList::ProcessAppendedItems() {
     items_.clear();
 }
 
+void DisplayItemList::RemoveLast() {
+  // We cannot remove the last item if it has been squashed into a picture.
+  // The last item should not have been handled by ProcessAppendedItems, so we
+  // don't need to remove it from approximate_op_count_, etc.
+  DCHECK(retain_individual_display_items_);
+  DCHECK(!use_cached_picture_);
+  items_.RemoveLast();
+}
+
 void DisplayItemList::Finalize() {
   ProcessAppendedItems();