Use mozjs tracing infrastructure (#29918)

* Update mozjs

https://github.com/servo/mozjs/commit/64711ec2e6dc4595df691bffc7f1e5052ab86c8d also fixes https://github.com/servo/servo/issues/30043

* Move to mozjs Traceable and introduce CustomTraceable

17 files changed, 68 insertions, 371 deletions

diff --git a/components/script/dom/bindings/record.rs b/components/script/dom/bindings/record.rs
index a586f9369c9..e5a796f5478 100644
--- a/components/script/dom/bindings/record.rs
+++ b/components/script/dom/bindings/record.rs
@@ -81,6 +81,7 @@ impl RecordKey for ByteString {
 /// The `Record` (open-ended dictionary) type.
 #[derive(Clone, JSTraceable)]
 pub struct Record<K: RecordKey, V> {
+    #[custom_trace]
     map: IndexMap<K, V>,
 }
 
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index 2eaad330108..e3c30c943ab 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -46,32 +46,23 @@ use crate::script_thread::IncompleteParserContexts;
 use crate::task::TaskBox;
 use indexmap::IndexMap;
 use js::glue::{CallObjectTracer, CallScriptTracer, CallStringTracer, CallValueTracer};
-use js::jsapi::{
-    GCTraceKindToAscii, Heap, JSObject, JSScript, JSString, JSTracer, JobQueue, TraceKind,
-};
+use js::jsapi::{GCTraceKindToAscii, Heap, JSObject, JSScript, JSString, JSTracer, TraceKind};
 use js::jsval::JSVal;
-use js::rust::{GCMethods, Handle, Runtime, Stencil};
-use js::typedarray::TypedArray;
-use js::typedarray::TypedArrayElement;
+use js::rust::{GCMethods, Handle};
+
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use parking_lot::RwLock;
 use servo_arc::Arc as ServoArc;
 use smallvec::SmallVec;
-use std::borrow::Cow;
-use std::cell::{Cell, RefCell, UnsafeCell};
+
 use std::collections::hash_map::RandomState;
-use std::collections::{BTreeMap, HashMap, HashSet, VecDeque};
+use std::collections::HashMap;
 use std::fmt::Display;
 use std::hash::{BuildHasher, Hash};
 use std::mem;
-use std::num::NonZeroU64;
-use std::ops::{Deref, DerefMut, Range};
-use std::path::PathBuf;
-use std::rc::Rc;
-use std::sync::atomic::{AtomicBool, AtomicUsize};
-use std::sync::Arc;
-use std::thread::JoinHandle;
-use std::time::{Instant, SystemTime};
+
+use std::ops::{Deref, DerefMut};
+
 use style::author_styles::AuthorStyles;
 use style::stylesheet_set::{AuthorStylesheetSet, DocumentStylesheetSet};
 use tendril::fmt::UTF8;
@@ -79,14 +70,28 @@ use tendril::stream::LossyDecoder;
 use tendril::TendrilSink;
 use webxr_api::{Finger, Hand};
 
-unsafe_no_jsmanaged_fields!(JoinHandle<()>);
-
 /// A trait to allow tracing (only) DOM objects.
-pub unsafe trait JSTraceable {
+pub use js::gc::Traceable as JSTraceable;
+
+/// A trait to allow tracing only DOM sub-objects.
+pub unsafe trait CustomTraceable {
     /// Trace `self`.
     unsafe fn trace(&self, trc: *mut JSTracer);
 }
 
+unsafe impl<T: CustomTraceable> CustomTraceable for Box<T> {
+    #[inline]
+    unsafe fn trace(&self, trc: *mut JSTracer) {
+        (**self).trace(trc);
+    }
+}
+
+unsafe impl<T: CustomTraceable> CustomTraceable for DomRefCell<T> {
+    unsafe fn trace(&self, trc: *mut JSTracer) {
+        (*self).borrow().trace(trc)
+    }
+}
+
 /// Wrapper type for nop traceble
 ///
 /// SAFETY: Inner type must not impl JSTraceable
@@ -236,10 +241,7 @@ unsafe_no_jsmanaged_fields!(IncompleteParserContexts);
 
 unsafe_no_jsmanaged_fields!(Reflector);
 
-unsafe_no_jsmanaged_fields!(*mut JobQueue);
-
-unsafe_no_jsmanaged_fields!(Cow<'static, str>);
-
+#[allow(dead_code)]
 /// Trace a `JSScript`.
 pub fn trace_script(tracer: *mut JSTracer, description: &str, script: &Heap<*mut JSScript>) {
     unsafe {
@@ -252,6 +254,7 @@ pub fn trace_script(tracer: *mut JSTracer, description: &str, script: &Heap<*mut
     }
 }
 
+#[allow(dead_code)]
 /// Trace a `JSVal`.
 pub fn trace_jsval(tracer: *mut JSTracer, description: &str, val: &Heap<JSVal>) {
     unsafe {
@@ -287,6 +290,7 @@ pub fn trace_object(tracer: *mut JSTracer, description: &str, obj: &Heap<*mut JS
     }
 }
 
+#[allow(dead_code)]
 /// Trace a `JSString`.
 pub fn trace_string(tracer: *mut JSTracer, description: &str, s: &Heap<*mut JSString>) {
     unsafe {
@@ -299,122 +303,25 @@ pub fn trace_string(tracer: *mut JSTracer, description: &str, s: &Heap<*mut JSSt
     }
 }
 
-unsafe impl<T: JSTraceable> JSTraceable for Rc<T> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        (**self).trace(trc)
-    }
-}
-
-unsafe impl<T: JSTraceable> JSTraceable for Arc<T> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        (**self).trace(trc)
-    }
-}
-
-unsafe impl<T: JSTraceable> JSTraceable for ServoArc<T> {
+unsafe impl<T: JSTraceable> CustomTraceable for ServoArc<T> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
         (**self).trace(trc)
     }
 }
 
-unsafe impl<T: JSTraceable> JSTraceable for RwLock<T> {
+unsafe impl<T: JSTraceable> CustomTraceable for RwLock<T> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
         self.read().trace(trc)
     }
 }
 
-unsafe impl<T: JSTraceable + ?Sized> JSTraceable for Box<T> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        (**self).trace(trc)
-    }
-}
-
-unsafe impl<T: JSTraceable> JSTraceable for [T] {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        for e in self.iter() {
-            e.trace(trc);
-        }
-    }
-}
-
-unsafe impl<T: JSTraceable + Copy> JSTraceable for Cell<T> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        self.get().trace(trc)
-    }
-}
-
-unsafe impl<T: JSTraceable> JSTraceable for UnsafeCell<T> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        (*self.get()).trace(trc)
-    }
-}
-
 unsafe impl<T: JSTraceable> JSTraceable for DomRefCell<T> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
         (*self).borrow().trace(trc)
     }
 }
 
-unsafe impl<T: JSTraceable> JSTraceable for RefCell<T> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        (*self).borrow().trace(trc)
-    }
-}
-
-unsafe impl JSTraceable for Heap<*mut JSScript> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        if self.get().is_null() {
-            return;
-        }
-        trace_script(trc, "heap script", self);
-    }
-}
-
-unsafe impl JSTraceable for Heap<*mut JSObject> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        if self.get().is_null() {
-            return;
-        }
-        trace_object(trc, "heap object", self);
-    }
-}
-
-unsafe impl JSTraceable for Heap<*mut JSString> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        if self.get().is_null() {
-            return;
-        }
-        trace_string(trc, "heap string", self);
-    }
-}
-
-unsafe impl JSTraceable for Heap<JSVal> {
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        trace_jsval(trc, "heap value", self);
-    }
-}
-
-// XXXManishearth Check if the following three are optimized to no-ops
-// if e.trace() is a no-op (e.g it is an unsafe_no_jsmanaged_fields type)
-unsafe impl<T: JSTraceable> JSTraceable for Vec<T> {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        for e in &*self {
-            e.trace(trc);
-        }
-    }
-}
-
-unsafe impl<T: JSTraceable> JSTraceable for VecDeque<T> {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        for e in &*self {
-            e.trace(trc);
-        }
-    }
-}
-
-unsafe impl<T: JSTraceable + Eq + Hash> JSTraceable for indexmap::IndexSet<T> {
+unsafe impl<T: JSTraceable + Eq + Hash> CustomTraceable for indexmap::IndexSet<T> {
     #[inline]
     unsafe fn trace(&self, trc: *mut JSTracer) {
         for e in self.iter() {
@@ -423,24 +330,9 @@ unsafe impl<T: JSTraceable + Eq + Hash> JSTraceable for indexmap::IndexSet<T> {
     }
 }
 
-unsafe impl<A, B, C, D> JSTraceable for (A, B, C, D)
-where
-    A: JSTraceable,
-    B: JSTraceable,
-    C: JSTraceable,
-    D: JSTraceable,
-{
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        self.0.trace(trc);
-        self.1.trace(trc);
-        self.2.trace(trc);
-        self.3.trace(trc);
-    }
-}
-
 // XXXManishearth Check if the following three are optimized to no-ops
 // if e.trace() is a no-op (e.g it is an unsafe_no_jsmanaged_fields type)
-unsafe impl<T: JSTraceable + 'static> JSTraceable for SmallVec<[T; 1]> {
+unsafe impl<T: JSTraceable + 'static> CustomTraceable for SmallVec<[T; 1]> {
     #[inline]
     unsafe fn trace(&self, trc: *mut JSTracer) {
         for e in self.iter() {
@@ -449,62 +341,7 @@ unsafe impl<T: JSTraceable + 'static> JSTraceable for SmallVec<[T; 1]> {
     }
 }
 
-unsafe impl<T: JSTraceable> JSTraceable for Option<T> {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        self.as_ref().map(|e| e.trace(trc));
-    }
-}
-
-unsafe impl<T: JSTraceable, U: JSTraceable> JSTraceable for Result<T, U> {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        match *self {
-            Ok(ref inner) => inner.trace(trc),
-            Err(ref inner) => inner.trace(trc),
-        }
-    }
-}
-
-unsafe impl<K, V, S> JSTraceable for HashMap<K, V, S>
-where
-    K: Hash + Eq + JSTraceable,
-    V: JSTraceable,
-    S: BuildHasher,
-{
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        for (k, v) in &*self {
-            k.trace(trc);
-            v.trace(trc);
-        }
-    }
-}
-
-unsafe impl<T, S> JSTraceable for HashSet<T, S>
-where
-    T: Hash + Eq + JSTraceable,
-    S: BuildHasher,
-{
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        for v in &*self {
-            v.trace(trc);
-        }
-    }
-}
-
-unsafe impl<K: Ord + JSTraceable, V: JSTraceable> JSTraceable for BTreeMap<K, V> {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        for (k, v) in self {
-            k.trace(trc);
-            v.trace(trc);
-        }
-    }
-}
-
-unsafe impl<K, V, S> JSTraceable for IndexMap<K, V, S>
+unsafe impl<K, V, S> CustomTraceable for IndexMap<K, V, S>
 where
     K: Hash + Eq + JSTraceable,
     V: JSTraceable,
@@ -519,69 +356,19 @@ where
     }
 }
 
-unsafe impl<A: JSTraceable, B: JSTraceable> JSTraceable for (A, B) {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        let (ref a, ref b) = *self;
-        a.trace(trc);
-        b.trace(trc);
-    }
-}
-
-unsafe impl<A: JSTraceable, B: JSTraceable, C: JSTraceable> JSTraceable for (A, B, C) {
-    #[inline]
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        let (ref a, ref b, ref c) = *self;
-        a.trace(trc);
-        b.trace(trc);
-        c.trace(trc);
-    }
-}
-
-unsafe_no_jsmanaged_fields!(bool, f32, f64, String, AtomicBool, AtomicUsize, char);
-unsafe_no_jsmanaged_fields!(usize, u8, u16, u32, u64);
-unsafe_no_jsmanaged_fields!(isize, i8, i16, i32, i64);
-unsafe_no_jsmanaged_fields!(NonZeroU64);
 unsafe_no_jsmanaged_fields!(Error);
 unsafe_no_jsmanaged_fields!(TrustedPromise);
 
-unsafe_no_jsmanaged_fields!(Runtime);
 unsafe_no_jsmanaged_fields!(ContextForRequestInterrupt);
 unsafe_no_jsmanaged_fields!(WindowProxyHandler);
 unsafe_no_jsmanaged_fields!(DOMString);
 unsafe_no_jsmanaged_fields!(USVString);
-unsafe_no_jsmanaged_fields!(SystemTime);
-unsafe_no_jsmanaged_fields!(Instant);
-unsafe_no_jsmanaged_fields!(PathBuf);
 unsafe_no_jsmanaged_fields!(WebGPUContextId);
 unsafe_no_jsmanaged_fields!(GPUBufferState);
 unsafe_no_jsmanaged_fields!(GPUCommandEncoderState);
-unsafe_no_jsmanaged_fields!(Range<u64>);
 unsafe_no_jsmanaged_fields!(SourceSet);
 unsafe_no_jsmanaged_fields!(HTMLMediaElementFetchContext);
 unsafe_no_jsmanaged_fields!(StreamConsumer);
-unsafe_no_jsmanaged_fields!(Stencil);
-
-unsafe impl<'a> JSTraceable for &'a str {
-    #[inline]
-    unsafe fn trace(&self, _: *mut JSTracer) {
-        // Do nothing
-    }
-}
-
-unsafe impl<A, B> JSTraceable for fn(A) -> B {
-    #[inline]
-    unsafe fn trace(&self, _: *mut JSTracer) {
-        // Do nothing
-    }
-}
-
-unsafe impl JSTraceable for () {
-    #[inline]
-    unsafe fn trace(&self, _: *mut JSTracer) {
-        // Do nothing
-    }
-}
 
 unsafe impl<T: DomObject> JSTraceable for Trusted<T> {
     #[inline]
@@ -590,16 +377,7 @@ unsafe impl<T: DomObject> JSTraceable for Trusted<T> {
     }
 }
 
-unsafe impl<T> JSTraceable for TypedArray<T, Box<Heap<*mut JSObject>>>
-where
-    T: TypedArrayElement,
-{
-    unsafe fn trace(&self, trc: *mut JSTracer) {
-        self.underlying_object().trace(trc);
-    }
-}
-
-unsafe impl<S> JSTraceable for DocumentStylesheetSet<S>
+unsafe impl<S> CustomTraceable for DocumentStylesheetSet<S>
 where
     S: JSTraceable + ::style::stylesheets::StylesheetInDocument + PartialEq + 'static,
 {
@@ -610,7 +388,7 @@ where
     }
 }
 
-unsafe impl<S> JSTraceable for AuthorStylesheetSet<S>
+unsafe impl<S> CustomTraceable for AuthorStylesheetSet<S>
 where
     S: JSTraceable + ::style::stylesheets::StylesheetInDocument + PartialEq + 'static,
 {
@@ -621,7 +399,7 @@ where
     }
 }
 
-unsafe impl<S> JSTraceable for AuthorStyles<S>
+unsafe impl<S> CustomTraceable for AuthorStyles<S>
 where
     S: JSTraceable + ::style::stylesheets::StylesheetInDocument + PartialEq + 'static,
 {
@@ -630,7 +408,7 @@ where
     }
 }
 
-unsafe impl<Sink> JSTraceable for LossyDecoder<Sink>
+unsafe impl<Sink> CustomTraceable for LossyDecoder<Sink>
 where
     Sink: JSTraceable + TendrilSink<UTF8>,
 {
@@ -639,7 +417,7 @@ where
     }
 }
 
-unsafe impl<J> JSTraceable for Hand<J>
+unsafe impl<J> CustomTraceable for Hand<J>
 where
     J: JSTraceable,
 {
@@ -669,7 +447,7 @@ where
     }
 }
 
-unsafe impl<J> JSTraceable for Finger<J>
+unsafe impl<J> CustomTraceable for Finger<J>
 where
     J: JSTraceable,
 {
@@ -692,47 +470,7 @@ where
 }
 
 /// Holds a set of JSTraceables that need to be rooted
-struct RootedTraceableSet {
-    set: Vec<*const dyn JSTraceable>,
-}
-
-thread_local!(
-    /// TLV Holds a set of JSTraceables that need to be rooted
-    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> = RefCell::new(RootedTraceableSet::new());
-);
-
-impl RootedTraceableSet {
-    fn new() -> RootedTraceableSet {
-        RootedTraceableSet { set: vec![] }
-    }
-
-    unsafe fn remove(traceable: *const dyn JSTraceable) {
-        ROOTED_TRACEABLES.with(|ref traceables| {
-            let mut traceables = traceables.borrow_mut();
-            let idx = match traceables
-                .set
-                .iter()
-                .rposition(|x| *x as *const () == traceable as *const ())
-            {
-                Some(idx) => idx,
-                None => unreachable!(),
-            };
-            traceables.set.remove(idx);
-        });
-    }
-
-    unsafe fn add(traceable: *const dyn JSTraceable) {
-        ROOTED_TRACEABLES.with(|ref traceables| {
-            traceables.borrow_mut().set.push(traceable);
-        })
-    }
-
-    unsafe fn trace(&self, tracer: *mut JSTracer) {
-        for traceable in &self.set {
-            (**traceable).trace(tracer);
-        }
-    }
-}
+pub use js::gc::RootedTraceableSet;
 
 /// Roots any JSTraceable thing
 ///
@@ -741,29 +479,23 @@ impl RootedTraceableSet {
 /// If you have an arbitrary number of DomObjects to root, use rooted_vec!.
 /// If you know what you're doing, use this.
 #[unrooted_must_root_lint::allow_unrooted_interior]
-pub struct RootedTraceableBox<T: 'static + JSTraceable> {
-    ptr: *mut T,
-}
+pub struct RootedTraceableBox<T: JSTraceable + 'static>(js::gc::RootedTraceableBox<T>);
 
 unsafe impl<T: JSTraceable + 'static> JSTraceable for RootedTraceableBox<T> {
     unsafe fn trace(&self, tracer: *mut JSTracer) {
-        (*self.ptr).trace(tracer);
+        self.0.trace(tracer);
     }
 }
 
 impl<T: JSTraceable + 'static> RootedTraceableBox<T> {
     /// DomRoot a JSTraceable thing for the life of this RootedTraceableBox
     pub fn new(traceable: T) -> RootedTraceableBox<T> {
-        Self::from_box(Box::new(traceable))
+        Self(js::gc::RootedTraceableBox::new(traceable))
     }
 
     /// Consumes a boxed JSTraceable and roots it for the life of this RootedTraceableBox.
     pub fn from_box(boxed_traceable: Box<T>) -> RootedTraceableBox<T> {
-        let traceable = Box::into_raw(boxed_traceable);
-        unsafe {
-            RootedTraceableSet::add(traceable);
-        }
-        RootedTraceableBox { ptr: traceable }
+        Self(js::gc::RootedTraceableBox::from_box(boxed_traceable))
     }
 }
 
@@ -773,7 +505,7 @@ where
     T: GCMethods + Copy,
 {
     pub fn handle(&self) -> Handle<T> {
-        unsafe { Handle::from_raw((*self.ptr).handle()) }
+        self.0.handle()
     }
 }
 
@@ -781,7 +513,7 @@ impl<T: JSTraceable + MallocSizeOf> MallocSizeOf for RootedTraceableBox<T> {
     fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
         // Briefly resurrect the real Box value so we can rely on the existing calculations.
         // Then immediately forget about it again to avoid dropping the box.
-        let inner = unsafe { Box::from_raw(self.ptr) };
+        let inner = unsafe { Box::from_raw(self.0.ptr()) };
         let size = inner.size_of(ops);
         mem::forget(inner);
         size
@@ -797,22 +529,13 @@ impl<T: JSTraceable + Default> Default for RootedTraceableBox<T> {
 impl<T: JSTraceable> Deref for RootedTraceableBox<T> {
     type Target = T;
     fn deref(&self) -> &T {
-        unsafe { &*self.ptr }
+        self.0.deref()
     }
 }
 
 impl<T: JSTraceable> DerefMut for RootedTraceableBox<T> {
     fn deref_mut(&mut self) -> &mut T {
-        unsafe { &mut *self.ptr }
-    }
-}
-
-impl<T: JSTraceable + 'static> Drop for RootedTraceableBox<T> {
-    fn drop(&mut self) {
-        unsafe {
-            RootedTraceableSet::remove(self.ptr);
-            let _ = Box::from_raw(self.ptr);
-        }
+        self.0.deref_mut()
     }
 }
 
@@ -847,7 +570,7 @@ impl<'a, T: 'static + JSTraceable> RootedVec<'a, T> {
         unsafe {
             RootedTraceableSet::add(root);
         }
-        RootedVec { root: root }
+        RootedVec { root }
     }
 }
 
@@ -862,7 +585,7 @@ impl<'a, T: 'static + JSTraceable + DomObject> RootedVec<'a, Dom<T>> {
             RootedTraceableSet::add(root);
         }
         root.v.extend(iter.map(|item| Dom::from_ref(&*item)));
-        RootedVec { root: root }
+        RootedVec { root }
     }
 }
 
@@ -887,12 +610,3 @@ impl<'a, T: JSTraceable> DerefMut for RootedVec<'a, T> {
         &mut self.root.v
     }
 }
-
-/// SM Callback that traces the rooted traceables
-pub unsafe fn trace_traceables(tracer: *mut JSTracer) {
-    trace!("tracing stack-rooted traceables");
-    ROOTED_TRACEABLES.with(|ref traceables| {
-        let traceables = traceables.borrow();
-        traceables.trace(tracer);
-    });
-}
diff --git a/components/script/dom/crypto.rs b/components/script/dom/crypto.rs
index 6aec75cbf3f..3fdcb93a9ec 100644
--- a/components/script/dom/crypto.rs
+++ b/components/script/dom/crypto.rs
@@ -17,13 +17,12 @@ use js::typedarray::ArrayBufferView;
 use servo_rand::{RngCore, ServoRng};
 use std::ptr::NonNull;
 
-unsafe_no_jsmanaged_fields!(ServoRng);
-
 // https://developer.mozilla.org/en-US/docs/Web/API/Crypto
 #[dom_struct]
 pub struct Crypto {
     reflector_: Reflector,
     #[ignore_malloc_size_of = "Defined in rand"]
+    #[no_trace]
     rng: DomRefCell<ServoRng>,
 }
 
diff --git a/components/script/dom/cssrulelist.rs b/components/script/dom/cssrulelist.rs
index 479c46c222e..0734f46abd1 100644
--- a/components/script/dom/cssrulelist.rs
+++ b/components/script/dom/cssrulelist.rs
@@ -25,8 +25,6 @@ use style::stylesheets::{
 
 unsafe_no_jsmanaged_fields!(RulesSource);
 
-unsafe_no_jsmanaged_fields!(CssRules);
-
 impl From<RulesMutateError> for Error {
     fn from(other: RulesMutateError) -> Self {
         match other {
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index aa7a2057503..c3d83be6966 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -269,6 +269,7 @@ pub struct Document {
     #[no_trace]
     style_shared_lock: StyleSharedRwLock,
     /// List of stylesheets associated with nodes in this document. |None| if the list needs to be refreshed.
+    #[custom_trace]
     stylesheets: DomRefCell<DocumentStylesheetSet<StyleSheetInDocument>>,
     stylesheet_list: MutNullableDom<StyleSheetList>,
     ready_state: Cell<DocumentReadyState>,
diff --git a/components/script/dom/keyboardevent.rs b/components/script/dom/keyboardevent.rs
index 8e31868fca8..f2f8084ce1d 100644
--- a/components/script/dom/keyboardevent.rs
+++ b/components/script/dom/keyboardevent.rs
@@ -19,16 +19,15 @@ use js::rust::HandleObject;
 use keyboard_types::{Key, Modifiers};
 use std::cell::Cell;
 
-unsafe_no_jsmanaged_fields!(Key);
-unsafe_no_jsmanaged_fields!(Modifiers);
-
 #[dom_struct]
 pub struct KeyboardEvent {
     uievent: UIEvent,
     key: DomRefCell<DOMString>,
+    #[no_trace]
     typed_key: DomRefCell<Key>,
     code: DomRefCell<DOMString>,
     location: Cell<u32>,
+    #[no_trace]
     modifiers: Cell<Modifiers>,
     repeat: Cell<bool>,
     is_composing: Cell<bool>,
diff --git a/components/script/dom/macros.rs b/components/script/dom/macros.rs
index 324f5419389..fd17d64d4f7 100644
--- a/components/script/dom/macros.rs
+++ b/components/script/dom/macros.rs
@@ -312,22 +312,6 @@ macro_rules! unsafe_no_jsmanaged_fields(
     );
 );
 
-macro_rules! jsmanaged_array(
-    ($count:expr) => (
-        #[allow(unsafe_code)]
-        unsafe impl<T> $crate::dom::bindings::trace::JSTraceable for [T; $count]
-            where T: $crate::dom::bindings::trace::JSTraceable
-        {
-            #[inline]
-            unsafe fn trace(&self, tracer: *mut ::js::jsapi::JSTracer) {
-                for v in self.iter() {
-                    v.trace(tracer);
-                }
-            }
-        }
-    );
-);
-
 /// These are used to generate a event handler which has no special case.
 macro_rules! define_event_handler(
     ($handler: ty, $event_type: ident, $getter: ident, $setter: ident, $setter_fn: ident) => (
diff --git a/components/script/dom/servoparser/html.rs b/components/script/dom/servoparser/html.rs
index fbf76473d27..3d1daad5424 100644
--- a/components/script/dom/servoparser/html.rs
+++ b/components/script/dom/servoparser/html.rs
@@ -7,7 +7,7 @@
 use crate::dom::bindings::codegen::Bindings::HTMLTemplateElementBinding::HTMLTemplateElementMethods;
 use crate::dom::bindings::inheritance::{Castable, CharacterDataTypeId, NodeTypeId};
 use crate::dom::bindings::root::{Dom, DomRoot};
-use crate::dom::bindings::trace::JSTraceable;
+use crate::dom::bindings::trace::{CustomTraceable, JSTraceable};
 use crate::dom::characterdata::CharacterData;
 use crate::dom::document::Document;
 use crate::dom::documentfragment::DocumentFragment;
@@ -101,7 +101,7 @@ impl Tokenizer {
 }
 
 #[allow(unsafe_code)]
-unsafe impl JSTraceable for HtmlTokenizer<TreeBuilder<Dom<Node>, Sink>> {
+unsafe impl CustomTraceable for HtmlTokenizer<TreeBuilder<Dom<Node>, Sink>> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
         struct Tracer(*mut JSTracer);
         let tracer = Tracer(trc);
diff --git a/components/script/dom/servoparser/mod.rs b/components/script/dom/servoparser/mod.rs
index 943a680d4ef..d8436b930bd 100644
--- a/components/script/dom/servoparser/mod.rs
+++ b/components/script/dom/servoparser/mod.rs
@@ -1381,6 +1381,7 @@ fn create_element_for_token(
 #[derive(JSTraceable, MallocSizeOf)]
 struct NetworkDecoder {
     #[ignore_malloc_size_of = "Defined in tendril"]
+    #[custom_trace]
     decoder: LossyDecoder<NetworkSink>,
 }
 
diff --git a/components/script/dom/servoparser/prefetch.rs b/components/script/dom/servoparser/prefetch.rs
index f328b417bd0..2f1da052978 100644
--- a/components/script/dom/servoparser/prefetch.rs
+++ b/components/script/dom/servoparser/prefetch.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::dom::bindings::reflector::DomObject;
-use crate::dom::bindings::trace::JSTraceable;
+use crate::dom::bindings::trace::{CustomTraceable, JSTraceable};
 use crate::dom::document::{determine_policy_for_token, Document};
 use crate::dom::htmlimageelement::{image_fetch_request, FromPictureOrSrcSet};
 use crate::dom::htmlscriptelement::script_fetch_request;
@@ -42,7 +42,7 @@ pub struct Tokenizer {
 }
 
 #[allow(unsafe_code)]
-unsafe impl JSTraceable for HtmlTokenizer<PrefetchSink> {
+unsafe impl CustomTraceable for HtmlTokenizer<PrefetchSink> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
         self.sink.trace(trc)
     }
diff --git a/components/script/dom/servoparser/xml.rs b/components/script/dom/servoparser/xml.rs
index 9b609cd7ea4..6ee1b464a6d 100644
--- a/components/script/dom/servoparser/xml.rs
+++ b/components/script/dom/servoparser/xml.rs
@@ -5,7 +5,7 @@
 #![allow(unrooted_must_root)]
 
 use crate::dom::bindings::root::{Dom, DomRoot};
-use crate::dom::bindings::trace::JSTraceable;
+use crate::dom::bindings::trace::{CustomTraceable, JSTraceable};
 use crate::dom::document::Document;
 use crate::dom::htmlscriptelement::HTMLScriptElement;
 use crate::dom::node::Node;
@@ -59,7 +59,7 @@ impl Tokenizer {
 }
 
 #[allow(unsafe_code)]
-unsafe impl JSTraceable for XmlTokenizer<XmlTreeBuilder<Dom<Node>, Sink>> {
+unsafe impl CustomTraceable for XmlTokenizer<XmlTreeBuilder<Dom<Node>, Sink>> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
         struct Tracer(*mut JSTracer);
         let tracer = Tracer(trc);
diff --git a/components/script/dom/shadowroot.rs b/components/script/dom/shadowroot.rs
index 1fa9faae287..24441391f94 100644
--- a/components/script/dom/shadowroot.rs
+++ b/components/script/dom/shadowroot.rs
@@ -42,6 +42,7 @@ pub struct ShadowRoot {
     document: Dom<Document>,
     host: MutNullableDom<Element>,
     /// List of author styles associated with nodes in this shadow tree.
+    #[custom_trace]
     author_styles: DomRefCell<AuthorStyles<StyleSheetInDocument>>,
     stylesheet_list: MutNullableDom<StyleSheetList>,
     window: Dom<Window>,
diff --git a/components/script/dom/webgltexture.rs b/components/script/dom/webgltexture.rs
index b4562e36e76..fc1610281c8 100644
--- a/components/script/dom/webgltexture.rs
+++ b/components/script/dom/webgltexture.rs
@@ -43,8 +43,6 @@ enum WebGLTextureOwner {
 const MAX_LEVEL_COUNT: usize = 31;
 const MAX_FACE_COUNT: usize = 6;
 
-jsmanaged_array!(MAX_LEVEL_COUNT * MAX_FACE_COUNT);
-
 #[dom_struct]
 pub struct WebGLTexture {
     webgl_object: WebGLObject,
diff --git a/components/script/dom/xrhand.rs b/components/script/dom/xrhand.rs
index a7457526242..1d04083c7aa 100644
--- a/components/script/dom/xrhand.rs
+++ b/components/script/dom/xrhand.rs
@@ -17,6 +17,7 @@ pub struct XRHand {
     #[ignore_malloc_size_of = "defined in webxr"]
     source: Dom<XRInputSource>,
     #[ignore_malloc_size_of = "partially defind in webxr"]
+    #[custom_trace]
     spaces: Hand<Dom<XRJointSpace>>,
 }
 
diff --git a/components/script/script_module.rs b/components/script/script_module.rs
index 01fe01e3472..f09ba9bf6c2 100644
--- a/components/script/script_module.rs
+++ b/components/script/script_module.rs
@@ -178,6 +178,7 @@ pub struct ModuleTree {
     // By default all maps in web specs are ordered maps
     // (https://infra.spec.whatwg.org/#ordered-map), however we can usually get away with using
     // stdlib maps and sets because we rarely iterate over them.
+    #[custom_trace]
     parent_identities: DomRefCell<IndexSet<ModuleIdentity>>,
     #[no_trace]
     descendant_urls: DomRefCell<IndexSet<ServoUrl>>,
diff --git a/components/script/script_runtime.rs b/components/script/script_runtime.rs
index 709b2891306..6dc1e24fd7c 100644
--- a/components/script/script_runtime.rs
+++ b/components/script/script_runtime.rs
@@ -22,7 +22,7 @@ use crate::dom::bindings::refcounted::{Trusted, TrustedPromise};
 use crate::dom::bindings::reflector::DomObject;
 use crate::dom::bindings::root::trace_roots;
 use crate::dom::bindings::settings_stack;
-use crate::dom::bindings::trace::{trace_traceables, JSTraceable};
+use crate::dom::bindings::trace::JSTraceable;
 use crate::dom::bindings::utils::DOM_CALLBACKS;
 use crate::dom::event::{Event, EventBubbles, EventCancelable, EventStatus};
 use crate::dom::eventtarget::EventTarget;
@@ -825,7 +825,6 @@ unsafe extern "C" fn trace_rust_roots(tr: *mut JSTracer, _data: *mut os::raw::c_
     }
     debug!("starting custom root handler");
     trace_thread(tr);
-    trace_traceables(tr);
     trace_roots(tr);
     trace_refcounted_objects(tr);
     settings_stack::trace(tr);
diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index e3051a0f8c2..b0b55eeb43a 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -521,8 +521,6 @@ impl<'a> Iterator for DocumentsIter<'a> {
 pub struct IncompleteParserContexts(RefCell<Vec<(PipelineId, ParserContext)>>);
 
 unsafe_no_jsmanaged_fields!(TaskQueue<MainThreadScriptMsg>);
-unsafe_no_jsmanaged_fields!(dyn BackgroundHangMonitorRegister);
-unsafe_no_jsmanaged_fields!(dyn BackgroundHangMonitor);
 
 #[derive(JSTraceable)]
 // ScriptThread instances are rooted on creation, so this is okay
@@ -552,8 +550,10 @@ pub struct ScriptThread {
     task_queue: TaskQueue<MainThreadScriptMsg>,
 
     /// A handle to register associated layout threads for hang-monitoring.
+    #[no_trace]
     background_hang_monitor_register: Box<dyn BackgroundHangMonitorRegister>,
     /// The dedicated means of communication with the background-hang-monitor for this script-thread.
+    #[no_trace]
     background_hang_monitor: Box<dyn BackgroundHangMonitor>,
     /// A flag set to `true` by the BHM on exit, and checked from within the interrupt handler.
     closing: Arc<AtomicBool>,