Auto merge of #9526 - schuster:node-remove, r=nox

My updates so far for issue #8465. See comments there for more information.

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components/script/dom/node.rs

@@ -1551,12 +1551,15 @@ impl Node {
                 Some(index)
             }
         };
-        // Step 6.
+        // Step 6. pre-removing steps for node iterators
+        // Step 7.
         let old_previous_sibling = node.GetPreviousSibling();
-        // Steps 7-8: mutation observers.
-        // Step 9.
+        // Step 8.
         let old_next_sibling = node.GetNextSibling();
+        // Steps 9-10 are handled in unbind_from_tree.
         parent.remove_child(node, cached_index);
+        // Step 11. transient registered observers
+        // Step 12.
         if let SuppressObserver::Unsuppressed = suppress_observers {
             vtable_for(&parent).children_changed(
                 &ChildrenMutation::replace(old_previous_sibling.r(),

components/script/dom/virtualmethods.rs

@@ -83,6 +83,8 @@ pub trait VirtualMethods {
 
     /// Called when a Node is removed from a tree, where 'tree_in_doc'
     /// indicates whether the tree is part of a Document.
+    /// Implements removing steps:
+    /// https://dom.spec.whatwg.org/#concept-node-remove-ext
     fn unbind_from_tree(&self, context: &UnbindContext) {
         if let Some(ref s) = self.super_type() {
             s.unbind_from_tree(context);