script: Use enums for event loop senders and receivers (#34896)

Previously, senders and receivers to different kinds of event loops (the
main `ScriptThread`, different types of workers) used a rust `trait`
mechanism to implement dynamic behavior. This led to having many unused
implementations of this `trait`. This change moves to using an `enum`
based approach for these senders and receivers and removes all of the
dead code.

In addition, to allowing for use of rust's dead code detection, it
simplifies the code a great deal. All of these generic senders and
receivers are moved to the `messaging.rs` file and given proper
documentation.

Finally, empty an `JSTraceable` implementation is made for all
crossbeam `Sender<...>`s to avoid having to manually skip them everytime
they are included in structs. The pre-existing empty `MallocSizeOf`
implementation is used more thoroughly.

Other unecessary wrappers around these senders and receivers are removed
as well.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/abstractworker.rs

@@ -7,7 +7,7 @@ use servo_url::ImmutableOrigin;
 
 use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::DomObject;
-use crate::script_runtime::CommonScriptMsg;
+use crate::messaging::CommonScriptMsg;
 
 /// Messages used to control the worker event loops
 pub enum WorkerScriptMsg {

components/script/dom/abstractworkerglobalscope.rs

@@ -2,88 +2,19 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use crossbeam_channel::{select, Receiver, Sender};
+use crossbeam_channel::{select, Receiver};
 use devtools_traits::DevtoolScriptControlMsg;
 
-use crate::dom::abstractworker::WorkerScriptMsg;
 use crate::dom::bindings::conversions::DerivedFrom;
 use crate::dom::bindings::reflector::DomObject;
-use crate::dom::dedicatedworkerglobalscope::{AutoWorkerReset, DedicatedWorkerScriptMsg};
+use crate::dom::dedicatedworkerglobalscope::AutoWorkerReset;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::worker::TrustedWorkerAddress;
 use crate::dom::workerglobalscope::WorkerGlobalScope;
 use crate::realms::enter_realm;
-use crate::script_runtime::{CanGc, CommonScriptMsg, ScriptChan, ScriptPort};
+use crate::script_runtime::CanGc;
 use crate::task_queue::{QueuedTaskConversion, TaskQueue};
 
-/// A ScriptChan that can be cloned freely and will silently send a TrustedWorkerAddress with
-/// common event loop messages. While this SendableWorkerScriptChan is alive, the associated
-/// Worker object will remain alive.
-#[derive(Clone, JSTraceable)]
-pub struct SendableWorkerScriptChan {
-    #[no_trace]
-    pub sender: Sender<DedicatedWorkerScriptMsg>,
-    pub worker: TrustedWorkerAddress,
-}
-
-impl ScriptChan for SendableWorkerScriptChan {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let msg = DedicatedWorkerScriptMsg::CommonWorker(
-            self.worker.clone(),
-            WorkerScriptMsg::Common(msg),
-        );
-        self.sender.send(msg).map_err(|_| ())
-    }
-
-    fn as_boxed(&self) -> Box<dyn ScriptChan> {
-        Box::new(SendableWorkerScriptChan {
-            sender: self.sender.clone(),
-            worker: self.worker.clone(),
-        })
-    }
-}
-
-/// A ScriptChan that can be cloned freely and will silently send a TrustedWorkerAddress with
-/// worker event loop messages. While this SendableWorkerScriptChan is alive, the associated
-/// Worker object will remain alive.
-#[derive(Clone, JSTraceable)]
-pub struct WorkerThreadWorkerChan {
-    #[no_trace]
-    pub sender: Sender<DedicatedWorkerScriptMsg>,
-    pub worker: TrustedWorkerAddress,
-}
-
-impl ScriptChan for WorkerThreadWorkerChan {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let msg = DedicatedWorkerScriptMsg::CommonWorker(
-            self.worker.clone(),
-            WorkerScriptMsg::Common(msg),
-        );
-        self.sender.send(msg).map_err(|_| ())
-    }
-
-    fn as_boxed(&self) -> Box<dyn ScriptChan> {
-        Box::new(WorkerThreadWorkerChan {
-            sender: self.sender.clone(),
-            worker: self.worker.clone(),
-        })
-    }
-}
-
-impl ScriptPort for Receiver<DedicatedWorkerScriptMsg> {
-    fn recv(&self) -> Result<CommonScriptMsg, ()> {
-        let common_msg = match self.recv() {
-            Ok(DedicatedWorkerScriptMsg::CommonWorker(_worker, common_msg)) => common_msg,
-            Err(_) => return Err(()),
-            Ok(DedicatedWorkerScriptMsg::WakeUp) => panic!("unexpected worker event message!"),
-        };
-        match common_msg {
-            WorkerScriptMsg::Common(script_msg) => Ok(script_msg),
-            WorkerScriptMsg::DOMMessage { .. } => panic!("unexpected worker event message!"),
-        }
-    }
-}
-
 pub trait WorkerEventLoopMethods {
     type WorkerMsg: QueuedTaskConversion + Send;
     type ControlMsg;

components/script/dom/bindings/refcounted.rs

@@ -53,7 +53,10 @@ mod dummy {
 pub use self::dummy::LIVE_REFERENCES;
 
 /// A pointer to a Rust DOM object that needs to be destroyed.
-struct TrustedReference(*const libc::c_void);
+#[derive(MallocSizeOf)]
+struct TrustedReference(
+    #[ignore_malloc_size_of = "This is a shared reference."] *const libc::c_void,
+);
 unsafe impl Send for TrustedReference {}
 
 impl TrustedReference {
@@ -158,10 +161,13 @@ impl TrustedPromise {
 /// DOM object is guaranteed to live at least as long as the last outstanding
 /// `Trusted<T>` instance.
 #[crown::unrooted_must_root_lint::allow_unrooted_interior]
+#[derive(MallocSizeOf)]
 pub struct Trusted<T: DomObject> {
     /// A pointer to the Rust DOM object of type T, but void to allow
     /// sending `Trusted<T>` between threads, regardless of T's sendability.
+    #[conditional_malloc_size_of]
     refcount: Arc<TrustedReference>,
+    #[ignore_malloc_size_of = "These are shared by all `Trusted` types."]
     owner_thread: *const LiveDOMReferences,
     phantom: PhantomData<T>,
 }

components/script/dom/bindings/trace.rs

@@ -37,6 +37,7 @@ use std::hash::{BuildHasher, Hash};
 use std::mem;
 use std::ops::{Deref, DerefMut};
 
+use crossbeam_channel::Sender;
 use indexmap::IndexMap;
 /// A trait to allow tracing (only) DOM objects.
 pub use js::gc::Traceable as JSTraceable;
@@ -107,6 +108,10 @@ unsafe impl<T: JSTraceable> CustomTraceable for OnceCell<T> {
     }
 }
 
+unsafe impl<T> CustomTraceable for Sender<T> {
+    unsafe fn trace(&self, _: *mut JSTracer) {}
+}
+
 /// Wrapper type for nop traceble
 ///
 /// SAFETY: Inner type must not impl JSTraceable

components/script/dom/dedicatedworkerglobalscope.rs

@@ -27,9 +27,7 @@ use style::thread_state::{self, ThreadState};
 
 use crate::devtools;
 use crate::dom::abstractworker::{SimpleWorkerErrorHandler, WorkerScriptMsg};
-use crate::dom::abstractworkerglobalscope::{
-    run_worker_event_loop, SendableWorkerScriptChan, WorkerEventLoopMethods, WorkerThreadWorkerChan,
-};
+use crate::dom::abstractworkerglobalscope::{run_worker_event_loop, WorkerEventLoopMethods};
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::DedicatedWorkerGlobalScopeBinding;
 use crate::dom::bindings::codegen::Bindings::DedicatedWorkerGlobalScopeBinding::DedicatedWorkerGlobalScopeMethods;
@@ -41,7 +39,7 @@ use crate::dom::bindings::reflector::DomObject;
 use crate::dom::bindings::root::{DomRoot, RootCollection, ThreadLocalStackRoots};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::bindings::structuredclone;
-use crate::dom::bindings::trace::RootedTraceableBox;
+use crate::dom::bindings::trace::{CustomTraceable, RootedTraceableBox};
 use crate::dom::errorevent::ErrorEvent;
 use crate::dom::event::{Event, EventBubbles, EventCancelable, EventStatus};
 use crate::dom::eventtarget::EventTarget;
@@ -52,12 +50,10 @@ use crate::dom::webgpu::identityhub::IdentityHub;
 use crate::dom::worker::{TrustedWorkerAddress, Worker};
 use crate::dom::workerglobalscope::WorkerGlobalScope;
 use crate::fetch::load_whole_resource;
+use crate::messaging::{CommonScriptMsg, ScriptEventLoopReceiver, ScriptEventLoopSender};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
 use crate::script_runtime::ScriptThreadEventCategory::WorkerEvent;
-use crate::script_runtime::{
-    CanGc, CommonScriptMsg, JSContext as SafeJSContext, Runtime, ScriptChan, ScriptPort,
-    ThreadSafeJSContext,
-};
+use crate::script_runtime::{CanGc, JSContext as SafeJSContext, Runtime, ThreadSafeJSContext};
 use crate::task_queue::{QueuedTask, QueuedTaskConversion, TaskQueue};
 use crate::task_source::{SendableTaskSource, TaskSourceName};
 
@@ -182,14 +178,12 @@ pub struct DedicatedWorkerGlobalScope {
     workerglobalscope: WorkerGlobalScope,
     #[ignore_malloc_size_of = "Defined in std"]
     task_queue: TaskQueue<DedicatedWorkerScriptMsg>,
-    #[ignore_malloc_size_of = "Defined in std"]
-    #[no_trace]
     own_sender: Sender<DedicatedWorkerScriptMsg>,
     #[ignore_malloc_size_of = "Trusted<T> has unclear ownership like Dom<T>"]
     worker: DomRefCell<Option<TrustedWorkerAddress>>,
     #[ignore_malloc_size_of = "Can't measure trait objects"]
     /// Sender to the parent thread.
-    parent_sender: Box<dyn ScriptChan>,
+    parent_event_loop_sender: ScriptEventLoopSender,
     #[ignore_malloc_size_of = "Arc"]
     #[no_trace]
     image_cache: Arc<dyn ImageCache>,
@@ -250,7 +244,7 @@ impl DedicatedWorkerGlobalScope {
         worker_url: ServoUrl,
         from_devtools_receiver: Receiver<DevtoolScriptControlMsg>,
         runtime: Runtime,
-        parent_sender: Box<dyn ScriptChan + Send>,
+        parent_event_loop_sender: ScriptEventLoopSender,
         own_sender: Sender<DedicatedWorkerScriptMsg>,
         receiver: Receiver<DedicatedWorkerScriptMsg>,
         closing: Arc<AtomicBool>,
@@ -273,7 +267,7 @@ impl DedicatedWorkerGlobalScope {
             ),
             task_queue: TaskQueue::new(receiver, own_sender.clone()),
             own_sender,
-            parent_sender,
+            parent_event_loop_sender,
             worker: DomRefCell::new(None),
             image_cache,
             browsing_context,
@@ -282,14 +276,14 @@ impl DedicatedWorkerGlobalScope {
     }
 
     #[allow(unsafe_code, clippy::too_many_arguments)]
-    pub fn new(
+    pub(crate) fn new(
         init: WorkerGlobalScopeInit,
         worker_name: DOMString,
         worker_type: WorkerType,
         worker_url: ServoUrl,
         from_devtools_receiver: Receiver<DevtoolScriptControlMsg>,
         runtime: Runtime,
-        parent_sender: Box<dyn ScriptChan + Send>,
+        parent_event_loop_sender: ScriptEventLoopSender,
         own_sender: Sender<DedicatedWorkerScriptMsg>,
         receiver: Receiver<DedicatedWorkerScriptMsg>,
         closing: Arc<AtomicBool>,
@@ -306,7 +300,7 @@ impl DedicatedWorkerGlobalScope {
             worker_url,
             from_devtools_receiver,
             runtime,
-            parent_sender,
+            parent_event_loop_sender,
             own_sender,
             receiver,
             closing,
@@ -321,12 +315,12 @@ impl DedicatedWorkerGlobalScope {
 
     /// <https://html.spec.whatwg.org/multipage/#run-a-worker>
     #[allow(unsafe_code, clippy::too_many_arguments)]
-    pub fn run_worker_scope(
+    pub(crate) fn run_worker_scope(
         mut init: WorkerGlobalScopeInit,
         worker_url: ServoUrl,
         from_devtools_receiver: IpcReceiver<DevtoolScriptControlMsg>,
         worker: TrustedWorkerAddress,
-        parent_sender: Box<dyn ScriptChan + Send>,
+        parent_event_loop_sender: ScriptEventLoopSender,
         own_sender: Sender<DedicatedWorkerScriptMsg>,
         receiver: Receiver<DedicatedWorkerScriptMsg>,
         worker_load_origin: WorkerScriptLoadOrigin,
@@ -379,10 +373,10 @@ impl DedicatedWorkerGlobalScope {
 
                 let runtime = unsafe {
                     let task_source = SendableTaskSource {
-                        sender: Box::new(WorkerThreadWorkerChan {
+                        sender: ScriptEventLoopSender::DedicatedWorker {
                             sender: own_sender.clone(),
-                            worker: worker.clone(),
-                        }),
+                            main_thread_worker: worker.clone(),
+                        },
                         pipeline_id,
                         name: TaskSourceName::Networking,
                         canceller: Default::default(),
@@ -417,7 +411,7 @@ impl DedicatedWorkerGlobalScope {
                     worker_url,
                     devtools_mpsc_port,
                     runtime,
-                    parent_sender.as_boxed(),
+                    parent_event_loop_sender.clone(),
                     own_sender,
                     receiver,
                     closing,
@@ -442,7 +436,7 @@ impl DedicatedWorkerGlobalScope {
                 ) {
                     Err(_) => {
                         println!("error loading script {}", serialized_worker_url);
-                        parent_sender
+                        parent_event_loop_sender
                             .send(CommonScriptMsg::Task(
                                 WorkerEvent,
                                 Box::new(SimpleWorkerErrorHandler::new(worker)),
@@ -491,7 +485,7 @@ impl DedicatedWorkerGlobalScope {
                             }
                         },
                         reporter_name,
-                        parent_sender,
+                        parent_event_loop_sender,
                         CommonScriptMsg::CollectReports,
                     );
 
@@ -526,21 +520,23 @@ impl DedicatedWorkerGlobalScope {
         self.image_cache.clone()
     }
 
-    pub(crate) fn event_loop_sender(&self) -> Option<Box<dyn ScriptChan + Send>> {
-        let worker = self.worker.borrow().clone()?;
-        Some(Box::new(WorkerThreadWorkerChan {
+    pub(crate) fn event_loop_sender(&self) -> Option<ScriptEventLoopSender> {
+        Some(ScriptEventLoopSender::DedicatedWorker {
             sender: self.own_sender.clone(),
-            worker,
-        }))
+            main_thread_worker: self.worker.borrow().clone()?,
+        })
     }
 
-    pub fn new_script_pair(&self) -> (Box<dyn ScriptChan + Send>, Box<dyn ScriptPort + Send>) {
-        let (tx, rx) = unbounded();
-        let chan = Box::new(SendableWorkerScriptChan {
-            sender: tx,
-            worker: self.worker.borrow().as_ref().unwrap().clone(),
-        });
-        (chan, Box::new(rx))
+    pub(crate) fn new_script_pair(&self) -> (ScriptEventLoopSender, ScriptEventLoopReceiver) {
+        let (sender, receiver) = unbounded();
+        let main_thread_worker = self.worker.borrow().as_ref().unwrap().clone();
+        (
+            ScriptEventLoopSender::DedicatedWorker {
+                sender,
+                main_thread_worker,
+            },
+            ScriptEventLoopReceiver::DedicatedWorker(receiver),
+        )
     }
 
     fn handle_script_event(&self, msg: WorkerScriptMsg, can_gc: CanGc) {
@@ -626,7 +622,7 @@ impl DedicatedWorkerGlobalScope {
                 global.report_an_error(error_info, HandleValue::null(), CanGc::note());
             }
         }));
-        self.parent_sender
+        self.parent_event_loop_sender
             .send(CommonScriptMsg::Task(
                 WorkerEvent,
                 task,
@@ -650,7 +646,7 @@ impl DedicatedWorkerGlobalScope {
         let task = Box::new(task!(post_worker_message: move || {
             Worker::handle_message(worker, data, CanGc::note());
         }));
-        self.parent_sender
+        self.parent_event_loop_sender
             .send(CommonScriptMsg::Task(
                 WorkerEvent,
                 task,

components/script/dom/document.rs

@@ -184,10 +184,10 @@ use crate::dom::windowproxy::WindowProxy;
 use crate::dom::xpathevaluator::XPathEvaluator;
 use crate::fetch::FetchCanceller;
 use crate::iframe_collection::IFrameCollection;
-use crate::messaging::MainThreadScriptMsg;
+use crate::messaging::{CommonScriptMsg, MainThreadScriptMsg};
 use crate::network_listener::{NetworkListener, PreInvoke};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
-use crate::script_runtime::{CanGc, CommonScriptMsg, ScriptThreadEventCategory};
+use crate::script_runtime::{CanGc, ScriptThreadEventCategory};
 use crate::script_thread::{with_script_thread, ScriptThread};
 use crate::stylesheet_set::StylesheetSetRef;
 use crate::task::TaskBox;

components/script/dom/globalscope.rs

@@ -128,13 +128,12 @@ use crate::dom::webgpu::identityhub::IdentityHub;
 use crate::dom::window::Window;
 use crate::dom::workerglobalscope::WorkerGlobalScope;
 use crate::dom::workletglobalscope::WorkletGlobalScope;
+use crate::messaging::{CommonScriptMsg, ScriptEventLoopReceiver, ScriptEventLoopSender};
 use crate::microtask::{Microtask, MicrotaskQueue, UserMicrotask};
 use crate::network_listener::{NetworkListener, PreInvoke};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
 use crate::script_module::{DynamicModuleList, ModuleScript, ModuleTree, ScriptFetchOptions};
-use crate::script_runtime::{
-    CanGc, CommonScriptMsg, JSContext as SafeJSContext, ScriptChan, ScriptPort, ThreadSafeJSContext,
-};
+use crate::script_runtime::{CanGc, JSContext as SafeJSContext, ThreadSafeJSContext};
 use crate::script_thread::{with_script_thread, ScriptThread};
 use crate::security_manager::CSPViolationReporter;
 use crate::task_manager::TaskManager;
@@ -2480,7 +2479,7 @@ impl GlobalScope {
     /// A sender to the event loop of this global scope. This either sends to the Worker event loop
     /// or the ScriptThread event loop in the case of a `Window`. This can be `None` for dedicated
     /// workers that are not currently handling a message.
-    pub(crate) fn event_loop_sender(&self) -> Option<Box<dyn ScriptChan + Send>> {
+    pub(crate) fn event_loop_sender(&self) -> Option<ScriptEventLoopSender> {
         if let Some(window) = self.downcast::<Window>() {
             Some(window.event_loop_sender())
         } else if let Some(dedicated) = self.downcast::<DedicatedWorkerGlobalScope>() {
@@ -2825,7 +2824,7 @@ impl GlobalScope {
     /// Create a new sender/receiver pair that can be used to implement an on-demand
     /// event loop. Used for implementing web APIs that require blocking semantics
     /// without resorting to nested event loops.
-    pub fn new_script_pair(&self) -> (Box<dyn ScriptChan + Send>, Box<dyn ScriptPort + Send>) {
+    pub(crate) fn new_script_pair(&self) -> (ScriptEventLoopSender, ScriptEventLoopReceiver) {
         if let Some(window) = self.downcast::<Window>() {
             return window.new_script_pair();
         }

components/script/dom/serviceworkerglobalscope.rs

@@ -33,6 +33,7 @@ use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::{DomRoot, RootCollection, ThreadLocalStackRoots};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::bindings::structuredclone;
+use crate::dom::bindings::trace::CustomTraceable;
 use crate::dom::dedicatedworkerglobalscope::AutoWorkerReset;
 use crate::dom::event::Event;
 use crate::dom::eventtarget::EventTarget;
@@ -44,10 +45,9 @@ use crate::dom::webgpu::identityhub::IdentityHub;
 use crate::dom::worker::TrustedWorkerAddress;
 use crate::dom::workerglobalscope::WorkerGlobalScope;
 use crate::fetch::load_whole_resource;
+use crate::messaging::{CommonScriptMsg, ScriptEventLoopSender};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
-use crate::script_runtime::{
-    CanGc, CommonScriptMsg, JSContext as SafeJSContext, Runtime, ScriptChan, ThreadSafeJSContext,
-};
+use crate::script_runtime::{CanGc, JSContext as SafeJSContext, Runtime, ThreadSafeJSContext};
 use crate::task_queue::{QueuedTask, QueuedTaskConversion, TaskQueue};
 use crate::task_source::TaskSourceName;
 
@@ -128,28 +128,6 @@ pub enum MixedMessage {
     Timer,
 }
 
-#[derive(Clone, JSTraceable)]
-pub struct ServiceWorkerChan {
-    #[no_trace]
-    pub sender: Sender<ServiceWorkerScriptMsg>,
-}
-
-impl ScriptChan for ServiceWorkerChan {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        self.sender
-            .send(ServiceWorkerScriptMsg::CommonWorker(
-                WorkerScriptMsg::Common(msg),
-            ))
-            .map_err(|_| ())
-    }
-
-    fn as_boxed(&self) -> Box<dyn ScriptChan> {
-        Box::new(ServiceWorkerChan {
-            sender: self.sender.clone(),
-        })
-    }
-}
-
 #[dom_struct]
 pub struct ServiceWorkerGlobalScope {
     workerglobalscope: WorkerGlobalScope,
@@ -158,8 +136,6 @@ pub struct ServiceWorkerGlobalScope {
     #[no_trace]
     task_queue: TaskQueue<ServiceWorkerScriptMsg>,
 
-    #[ignore_malloc_size_of = "Defined in std"]
-    #[no_trace]
     own_sender: Sender<ServiceWorkerScriptMsg>,
 
     /// A port on which a single "time-out" message can be received,
@@ -485,10 +461,8 @@ impl ServiceWorkerGlobalScope {
         }
     }
 
-    pub(crate) fn event_loop_sender(&self) -> Box<dyn ScriptChan + Send> {
-        Box::new(ServiceWorkerChan {
-            sender: self.own_sender.clone(),
-        })
+    pub(crate) fn event_loop_sender(&self) -> ScriptEventLoopSender {
+        ScriptEventLoopSender::ServiceWorker(self.own_sender.clone())
     }
 
     fn dispatch_activate(&self, can_gc: CanGc) {

components/script/dom/window.rs

@@ -112,7 +112,7 @@ use crate::dom::bindings::reflector::DomObject;
 use crate::dom::bindings::root::{Dom, DomRoot, MutNullableDom};
 use crate::dom::bindings::str::{DOMString, USVString};
 use crate::dom::bindings::structuredclone;
-use crate::dom::bindings::trace::{JSTraceable, RootedTraceableBox};
+use crate::dom::bindings::trace::{CustomTraceable, JSTraceable, RootedTraceableBox};
 use crate::dom::bindings::utils::GlobalStaticData;
 use crate::dom::bindings::weakref::DOMTracker;
 use crate::dom::bluetooth::BluetoothExtraPermissionData;
@@ -149,11 +149,11 @@ use crate::dom::worklet::Worklet;
 use crate::dom::workletglobalscope::WorkletGlobalScopeType;
 use crate::layout_image::fetch_image_for_layout;
 use crate::messaging::{
-    ImageCacheMsg, MainThreadScriptChan, MainThreadScriptMsg, SendableMainThreadScriptChan,
+    ImageCacheMsg, MainThreadScriptMsg, ScriptEventLoopReceiver, ScriptEventLoopSender,
 };
 use crate::microtask::MicrotaskQueue;
 use crate::realms::{enter_realm, InRealm};
-use crate::script_runtime::{CanGc, JSContext, Runtime, ScriptChan, ScriptPort};
+use crate::script_runtime::{CanGc, JSContext, Runtime};
 use crate::script_thread::ScriptThread;
 use crate::timers::{IsInterval, TimerCallback};
 use crate::unminify::unminified_path;
@@ -202,8 +202,7 @@ impl LayoutBlocker {
 #[dom_struct]
 pub struct Window {
     globalscope: GlobalScope,
-    #[ignore_malloc_size_of = "trait objects are hard"]
-    script_chan: MainThreadScriptChan,
+    script_chan: Sender<MainThreadScriptMsg>,
     #[no_trace]
     #[ignore_malloc_size_of = "TODO: Add MallocSizeOf support to layout"]
     layout: RefCell<Box<dyn Layout>>,
@@ -216,7 +215,6 @@ pub struct Window {
     #[ignore_malloc_size_of = "Arc"]
     #[no_trace]
     image_cache: Arc<dyn ImageCache>,
-    #[ignore_malloc_size_of = "channels are hard"]
     #[no_trace]
     image_cache_chan: Sender<ImageCacheMsg>,
     window_proxy: MutNullableDom<WindowProxy>,
@@ -452,16 +450,23 @@ impl Window {
     }
 
     pub(crate) fn main_thread_script_chan(&self) -> &Sender<MainThreadScriptMsg> {
-        &self.script_chan.0
+        &self.script_chan
     }
 
     pub fn parent_info(&self) -> Option<PipelineId> {
         self.parent_info
     }
 
-    pub fn new_script_pair(&self) -> (Box<dyn ScriptChan + Send>, Box<dyn ScriptPort + Send>) {
-        let (tx, rx) = unbounded();
-        (Box::new(SendableMainThreadScriptChan(tx)), Box::new(rx))
+    pub(crate) fn new_script_pair(&self) -> (ScriptEventLoopSender, ScriptEventLoopReceiver) {
+        let (sender, receiver) = unbounded();
+        (
+            ScriptEventLoopSender::MainThread(sender),
+            ScriptEventLoopReceiver::MainThread(receiver),
+        )
+    }
+
+    pub(crate) fn event_loop_sender(&self) -> ScriptEventLoopSender {
+        ScriptEventLoopSender::MainThread(self.script_chan.clone())
     }
 
     pub fn image_cache(&self) -> Arc<dyn ImageCache> {
@@ -2677,7 +2682,7 @@ impl Window {
     #[allow(clippy::too_many_arguments)]
     pub(crate) fn new(
         runtime: Rc<Runtime>,
-        script_chan: MainThreadScriptChan,
+        script_chan: Sender<MainThreadScriptMsg>,
         layout: Box<dyn Layout>,
         font_context: Arc<FontContext>,
         image_cache_chan: Sender<ImageCacheMsg>,
@@ -2803,10 +2808,6 @@ impl Window {
         unsafe { WindowBinding::Wrap(JSContext::from_ptr(runtime.cx()), win) }
     }
 
-    pub(crate) fn event_loop_sender(&self) -> Box<dyn ScriptChan + Send> {
-        Box::new(self.script_chan.clone())
-    }
-
     pub(crate) fn pipeline_id(&self) -> PipelineId {
         self.as_global_scope().pipeline_id()
     }

components/script/dom/worker.rs

@@ -28,7 +28,7 @@ use crate::dom::bindings::reflector::{reflect_dom_object_with_proto, DomObject};
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::str::USVString;
 use crate::dom::bindings::structuredclone;
-use crate::dom::bindings::trace::RootedTraceableBox;
+use crate::dom::bindings::trace::{CustomTraceable, RootedTraceableBox};
 use crate::dom::dedicatedworkerglobalscope::{
     DedicatedWorkerGlobalScope, DedicatedWorkerScriptMsg,
 };
@@ -47,8 +47,6 @@ pub type TrustedWorkerAddress = Trusted<Worker>;
 #[dom_struct]
 pub struct Worker {
     eventtarget: EventTarget,
-    #[ignore_malloc_size_of = "Defined in std"]
-    #[no_trace]
     /// Sender to the Receiver associated with the DedicatedWorkerGlobalScope
     /// this Worker created.
     sender: Sender<DedicatedWorkerScriptMsg>,

components/script/dom/workerglobalscope.rs

@@ -56,8 +56,9 @@ use crate::dom::window::{base64_atob, base64_btoa};
 use crate::dom::workerlocation::WorkerLocation;
 use crate::dom::workernavigator::WorkerNavigator;
 use crate::fetch;
+use crate::messaging::{CommonScriptMsg, ScriptEventLoopReceiver, ScriptEventLoopSender};
 use crate::realms::{enter_realm, InRealm};
-use crate::script_runtime::{CanGc, CommonScriptMsg, JSContext, Runtime, ScriptChan, ScriptPort};
+use crate::script_runtime::{CanGc, JSContext, Runtime};
 use crate::task::TaskCanceller;
 use crate::timers::{IsInterval, TimerCallback};
 
@@ -491,7 +492,7 @@ impl WorkerGlobalScope {
         }
     }
 
-    pub fn new_script_pair(&self) -> (Box<dyn ScriptChan + Send>, Box<dyn ScriptPort + Send>) {
+    pub(crate) fn new_script_pair(&self) -> (ScriptEventLoopSender, ScriptEventLoopReceiver) {
         let dedicated = self.downcast::<DedicatedWorkerGlobalScope>();
         if let Some(dedicated) = dedicated {
             dedicated.new_script_pair()

components/script/dom/worklet.rs

@@ -49,9 +49,9 @@ use crate::dom::workletglobalscope::{
     WorkletGlobalScope, WorkletGlobalScopeInit, WorkletGlobalScopeType, WorkletTask,
 };
 use crate::fetch::load_whole_resource;
-use crate::messaging::MainThreadScriptMsg;
+use crate::messaging::{CommonScriptMsg, MainThreadScriptMsg};
 use crate::realms::InRealm;
-use crate::script_runtime::{CanGc, CommonScriptMsg, Runtime, ScriptThreadEventCategory};
+use crate::script_runtime::{CanGc, Runtime, ScriptThreadEventCategory};
 use crate::script_thread::ScriptThread;
 use crate::task::TaskBox;
 use crate::task_source::TaskSourceName;
@@ -768,7 +768,6 @@ impl WorkletThread {
 #[derive(Clone, JSTraceable, MallocSizeOf)]
 pub struct WorkletExecutor {
     worklet_id: WorkletId,
-    #[ignore_malloc_size_of = "channels are hard"]
     #[no_trace]
     primary_sender: Sender<WorkletData>,
 }

components/script/dom/workletglobalscope.rs

@@ -21,6 +21,7 @@ use servo_url::{ImmutableOrigin, MutableOrigin, ServoUrl};
 
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::trace::CustomTraceable;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::paintworkletglobalscope::{PaintWorkletGlobalScope, PaintWorkletTask};
 use crate::dom::testworkletglobalscope::{TestWorkletGlobalScope, TestWorkletTask};
@@ -40,8 +41,6 @@ pub struct WorkletGlobalScope {
     #[no_trace]
     base_url: ServoUrl,
     /// Sender back to the script thread
-    #[ignore_malloc_size_of = "channels are hard"]
-    #[no_trace]
     to_script_thread_sender: Sender<MainThreadScriptMsg>,
     /// Worklet task executor
     executor: WorkletExecutor,