From faa581be86e0a47c443c100a1e851ca442fb01bd Mon Sep 17 00:00:00 2001
From: Anthony Ramine <n.oxyde@gmail.com>
Date: Thu, 27 Aug 2015 13:39:47 +0200
Subject: [PATCH] Optimise most basic case of .replaceChild() when updating
 childNodes

---
 components/script/dom/nodelist.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/components/script/dom/nodelist.rs b/components/script/dom/nodelist.rs
index eb3353a4d6e..514221f850d 100644
--- a/components/script/dom/nodelist.rs
+++ b/components/script/dom/nodelist.rs
@@ -218,7 +218,10 @@ impl ChildrenList {
                     },
                 };
                 list.last_visited.set(Some(JS::from_ref(visited)));
-            } else {
+            } else if added.len() != 1 {
+                // The replaced child isn't the last visited one, and there are
+                // 0 or more than 1 nodes to replace it. Special care must be
+                // given to update the state of that ChildrenList.
                 match (prev, next) {
                     (Some(_), None) => {},
                     (None, Some(next)) => {