Auto merge of #12862 - servo:layout-new, r=emilio

added dom obj counting to decide sequential/parallel layout (#10110)

This is a rebased version of #11713

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #10110 (github issue number if applicable).
- [X] There are no tests for these changes because it's an optimization with no visible behavioral changes

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1 files changed, 6 insertions, 2 deletions

diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index c384001e33a..6df2122e7b3 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -2151,10 +2151,12 @@ impl VirtualMethods for Element {
             return;
         }
 
+        let doc = document_from_node(self);
         if let Some(ref value) = *self.id_attribute.borrow() {
-            let doc = document_from_node(self);
             doc.register_named_element(self, value.clone());
         }
+        // This is used for layout optimization.
+        doc.increment_dom_count();
     }
 
     fn unbind_from_tree(&self, context: &UnbindContext) {
@@ -2164,10 +2166,12 @@ impl VirtualMethods for Element {
             return;
         }
 
+        let doc = document_from_node(self);
         if let Some(ref value) = *self.id_attribute.borrow() {
-            let doc = document_from_node(self);
             doc.unregister_named_element(self, value.clone());
         }
+        // This is used for layout optimization.
+        doc.decrement_dom_count();
     }
 
     fn children_changed(&self, mutation: &ChildrenMutation) {