cc: Implement RemoveLast for DisplayItemList.

cc/playback/display_item_list.h

Index: cc/playback/display_item_list.h
diff --git a/cc/playback/display_item_list.h b/cc/playback/display_item_list.h
index 79d38f5ddb1dab61dca00f34d10f3acaaddff90d..c238daa67c2da810ab1ffaeffa72c3e154cc0132 100644
--- a/cc/playback/display_item_list.h
+++ b/cc/playback/display_item_list.h
@@ -53,6 +53,11 @@ class CC_EXPORT DisplayItemList
     return items_.AllocateAndConstruct<DisplayItemType>();
   }
 
+  // Removes the last item. This cannot be called on lists with cached pictures
+  // (since the data may already have been incorporated into cached picture
+  // sizes, etc).
+  void RemoveLast();
+
   // Called after all items are appended, to process the items and, if
   // applicable, create an internally cached SkPicture.
   void Finalize();