No tracing of nop traceable fields (#29926)

* Add `no_trace` option to JSTraceable derive

* NoTrace wrapper

* Port some types to no_trace schematics

* Fixing my unsafe mistakes (not tracing traceables)

* Add docs & safety guards for no_trace

Safety guards (trait shenanigans) guarantees safety usage of `no_trace`

* Port canvas_traits to no_trace

* Port servo_media to no_trace

* Port net_traits to no_trace

* Port style to no_trace

* Port webgpu to no_trace

* Port script_traits to no_trace

* Port canvas_traits, devtools_traits, embedder_traits, profile_traits to no_trace

* unrooted_must_root lint in seperate file

* Add trace_in_no_trace_lint as script_plugin

* Composable types in must_not_have_traceable

* Introduced HashMapTracedValues wrapper

* `HashMap<NoTrace<K>,V>`->`HashMapTracedValues<K,V>`

* Port rest of servo's types to no_trace

* Port html5ever, euclid, mime and http to no_trace

* Port remaining externals to no_trace

* Port webxr and Arc<Mutex<_>>

* Fix spelling in notrace doc

1 files changed, 9 insertions, 0 deletions

diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 7408147893f..3304e23cb64 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -149,23 +149,31 @@ use xml5ever::serialize::TraversalScope::IncludeNode as XmlIncludeNode;
 #[dom_struct]
 pub struct Element {
     node: Node,
+    #[no_trace]
     local_name: LocalName,
     tag_name: TagName,
+    #[no_trace]
     namespace: Namespace,
+    #[no_trace]
     prefix: DomRefCell<Option<Prefix>>,
     attrs: DomRefCell<Vec<Dom<Attr>>>,
+    #[no_trace]
     id_attribute: DomRefCell<Option<Atom>>,
+    #[no_trace]
     is: DomRefCell<Option<LocalName>>,
     #[ignore_malloc_size_of = "Arc"]
+    #[no_trace]
     style_attribute: DomRefCell<Option<Arc<Locked<PropertyDeclarationBlock>>>>,
     attr_list: MutNullableDom<NamedNodeMap>,
     class_list: MutNullableDom<DOMTokenList>,
+    #[no_trace]
     state: Cell<ElementState>,
     /// These flags are set by the style system to indicate the that certain
     /// operations may require restyling this element or its descendants. The
     /// flags are not atomic, so the style system takes care of only set them
     /// when it has exclusive access to the element.
     #[ignore_malloc_size_of = "bitflags defined in rust-selectors"]
+    #[no_trace]
     selector_flags: Cell<ElementSelectorFlags>,
     rare_data: DomRefCell<Option<Box<ElementRareData>>>,
 }
@@ -3673,6 +3681,7 @@ impl<'a> AttributeMutation<'a> {
 /// owner changes.
 #[derive(JSTraceable, MallocSizeOf)]
 struct TagName {
+    #[no_trace]
     ptr: DomRefCell<Option<LocalName>>,
 }