Fix step 14.2 of Range::ExtractContents

We need the last inclusive ancestor of start node that is not an inclusive ancestor
of end node, not the first that is an inclusive ancestor of it.

1 files changed, 3 insertions, 2 deletions

diff --git a/components/script/dom/range.rs b/components/script/dom/range.rs
index 88fc9ad35bc..c6efae90b98 100644
--- a/components/script/dom/range.rs
+++ b/components/script/dom/range.rs
@@ -564,8 +564,9 @@ impl RangeMethods for Range {
         } else {
             // Step 14.1-2.
             let reference_node = start_node.ancestors()
-                                           .find(|n| n.is_inclusive_ancestor_of(end_node.r()))
-                                           .unwrap();
+                                           .take_while(|n| !n.is_inclusive_ancestor_of(&end_node))
+                                           .last()
+                                           .unwrap_or(Root::from_ref(&start_node));
             // Step 14.3.
             (reference_node.GetParentNode().unwrap(), reference_node.index() + 1)
         };