Implement NonDocumentTypeChildNode::*ElementSibling()

1 files changed, 7 insertions, 0 deletions

diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 55d60966b27..5368a012846 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -415,6 +415,7 @@ pub trait NodeHelpers<'a> {
     fn rev_children(self) -> ReverseChildrenIterator;
     fn child_elements(self) -> ChildElementIterator;
     fn following_siblings(self) -> NodeChildrenIterator;
+    fn preceding_siblings(self) -> ReverseChildrenIterator;
     fn is_in_doc(self) -> bool;
     fn is_inclusive_ancestor_of(self, parent: JSRef<Node>) -> bool;
     fn is_parent_of(self, child: JSRef<Node>) -> bool;
@@ -764,6 +765,12 @@ impl<'a> NodeHelpers<'a> for JSRef<'a, Node> {
         }
     }
 
+    fn preceding_siblings(self) -> ReverseChildrenIterator {
+        ReverseChildrenIterator {
+            current: self.prev_sibling(),
+        }
+    }
+
     fn is_parent_of(self, child: JSRef<Node>) -> bool {
         match child.parent_node() {
             Some(ref parent) if parent == &Temporary::from_rooted(self) => true,