Force all messages to worker tasks to send a TrustedWorkerAddress along with the ScriptMsg. This ensures that the main-thread Worker object is rooted for as long as there are events in flight or being processed.

components/script/dom/bindings/global.rs

@@ -10,7 +10,7 @@
 use dom::bindings::conversions::FromJSValConvertible;
 use dom::bindings::js::{JS, JSRef, Root};
 use dom::bindings::utils::{Reflectable, Reflector};
-use dom::workerglobalscope::WorkerGlobalScope;
+use dom::workerglobalscope::{WorkerGlobalScope, WorkerGlobalScopeHelpers};
 use dom::window;
 use script_task::ScriptChan;
 
@@ -81,7 +81,7 @@ impl<'a> GlobalRef<'a> {
 
     /// `ScriptChan` used to send messages to the event loop of this global's
     /// thread.
-    pub fn script_chan<'b>(&'b self) -> &'b ScriptChan {
+    pub fn script_chan(&self) -> Box<ScriptChan+Send> {
         match *self {
             GlobalRef::Window(ref window) => window.script_chan(),
             GlobalRef::Worker(ref worker) => worker.script_chan(),

components/script/dom/bindings/refcounted.rs

@@ -42,32 +42,37 @@ local_data_key!(pub LiveReferences: LiveDOMReferences)
 /// DOM object is guaranteed to live at least as long as the last outstanding
 /// `Trusted<T>` instance.
 pub struct Trusted<T> {
-    cx: *mut JSContext,
     /// A pointer to the Rust DOM object of type T, but void to allow
     /// sending `Trusted<T>` between tasks, regardless of T's sendability.
     ptr: *const libc::c_void,
     refcount: Arc<Mutex<uint>>,
-    script_chan: ScriptChan,
+    script_chan: Box<ScriptChan + Send>,
+    owner_thread: *const libc::c_void,
 }
 
 impl<T: Reflectable> Trusted<T> {
     /// Create a new `Trusted<T>` instance from an existing DOM pointer. The DOM object will
     /// be prevented from being GCed for the duration of the resulting `Trusted<T>` object's
     /// lifetime.
-    pub fn new(cx: *mut JSContext, ptr: JSRef<T>, script_chan: ScriptChan) -> Trusted<T> {
+    pub fn new(cx: *mut JSContext, ptr: JSRef<T>, script_chan: Box<ScriptChan + Send>) -> Trusted<T> {
         let live_references = LiveReferences.get().unwrap();
         let refcount = live_references.addref(cx, &*ptr as *const T);
         Trusted {
-            cx: cx,
             ptr: &*ptr as *const T as *const libc::c_void,
             refcount: refcount,
             script_chan: script_chan,
+            owner_thread: (&*live_references) as *const _ as *const libc::c_void,
         }
     }
 
-    /// Obtain a usable DOM pointer from a pinned `Trusted<T>` value. Attempts to use the
+    /// Obtain a usable DOM pointer from a pinned `Trusted<T>` value. Fails if used on
-    /// resulting `Temporary<T>` off of the script thread will fail.
+    /// a different thread than the original value from which this `Trusted<T>` was
+    /// obtained.
     pub fn to_temporary(&self) -> Temporary<T> {
+        assert!({
+            let live_references = LiveReferences.get().unwrap();
+            self.owner_thread == (&*live_references) as *const _ as *const libc::c_void
+        });
         unsafe {
             Temporary::new(JS::from_raw(self.ptr as *const T))
         }
@@ -82,10 +87,10 @@ impl<T: Reflectable> Clone for Trusted<T> {
         }
 
         Trusted {
-            cx: self.cx,
             ptr: self.ptr,
             refcount: self.refcount.clone(),
             script_chan: self.script_chan.clone(),
+            owner_thread: self.owner_thread,
         }
     }
 }
@@ -97,8 +102,7 @@ impl<T: Reflectable> Drop for Trusted<T> {
         assert!(*refcount > 0);
         *refcount -= 1;
         if *refcount == 0 {
-            let ScriptChan(ref chan) = self.script_chan;
+            self.script_chan.send(ScriptMsg::RefcountCleanup(self.ptr));
-            chan.send(ScriptMsg::RefcountCleanup(self.ptr));
         }
     }
 }

components/script/dom/bindings/trace.rs

@@ -31,6 +31,7 @@ use dom::bindings::js::JS;
 use dom::bindings::refcounted::Trusted;
 use dom::bindings::utils::{Reflectable, Reflector, WindowProxyHandler};
 use dom::node::{Node, TrustedNodeAddress};
+use script_task::ScriptChan;
 
 use collections::hash::{Hash, Hasher};
 use cssparser::RGBA;
@@ -219,6 +220,13 @@ no_jsmanaged_fields!(UntrustedNodeAddress)
 no_jsmanaged_fields!(LengthOrPercentageOrAuto)
 no_jsmanaged_fields!(RGBA)
 
+impl JSTraceable for Box<ScriptChan+Send> {
+    #[inline]
+    fn trace(&self, _trc: *mut JSTracer) {
+        // Do nothing
+    }
+}
+
 impl<'a> JSTraceable for &'a str {
     #[inline]
     fn trace(&self, _: *mut JSTracer) {

components/script/dom/dedicatedworkerglobalscope.rs

@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::DedicatedWorkerGlobalScopeBinding;
 use dom::bindings::codegen::Bindings::DedicatedWorkerGlobalScopeBinding::DedicatedWorkerGlobalScopeMethods;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::EventHandlerNonNull;
@@ -35,44 +36,93 @@ use std::rc::Rc;
 use std::ptr;
 use url::Url;
 
+/// A ScriptChan that can be cloned freely and will silently send a TrustedWorkerAddress with
+/// every message. While this SendableWorkerScriptChan is alive, the associated Worker object
+/// will remain alive.
+#[deriving(Clone)]
+#[jstraceable]
+pub struct SendableWorkerScriptChan {
+    sender: Sender<(TrustedWorkerAddress, ScriptMsg)>,
+    worker: TrustedWorkerAddress,
+}
+
+impl ScriptChan for SendableWorkerScriptChan {
+    fn send(&self, msg: ScriptMsg) {
+        self.sender.send((self.worker.clone(), msg));
+    }
+
+    fn clone(&self) -> Box<ScriptChan + Send> {
+        box SendableWorkerScriptChan {
+            sender: self.sender.clone(),
+            worker: self.worker.clone(),
+        }
+    }
+}
+
+/// Set the `worker` field of a related DedicatedWorkerGlobalScope object to a particular
+/// value for the duration of this object's lifetime. This ensures that the related Worker
+/// object only lives as long as necessary (ie. while events are being executed), while
+/// providing a reference that can be cloned freely.
+struct AutoWorkerReset<'a> {
+    workerscope: JSRef<'a, DedicatedWorkerGlobalScope>,
+    old_worker: Option<TrustedWorkerAddress>,
+}
+
+impl<'a> AutoWorkerReset<'a> {
+    fn new(workerscope: JSRef<'a, DedicatedWorkerGlobalScope>, worker: TrustedWorkerAddress) -> AutoWorkerReset<'a> {
+        let reset = AutoWorkerReset {
+            workerscope: workerscope,
+            old_worker: workerscope.worker.borrow().clone()
+        };
+        *workerscope.worker.borrow_mut() = Some(worker);
+        reset
+    }
+}
+
+#[unsafe_destructor]
+impl<'a> Drop for AutoWorkerReset<'a> {
+    fn drop(&mut self) {
+        *self.workerscope.worker.borrow_mut() = self.old_worker.clone();
+    }
+}
+
 #[dom_struct]
 pub struct DedicatedWorkerGlobalScope {
     workerglobalscope: WorkerGlobalScope,
-    receiver: Receiver<ScriptMsg>,
+    receiver: Receiver<(TrustedWorkerAddress, ScriptMsg)>,
+    own_sender: Sender<(TrustedWorkerAddress, ScriptMsg)>,
+    worker: DOMRefCell<Option<TrustedWorkerAddress>>,
     /// Sender to the parent thread.
-    parent_sender: ScriptChan,
+    parent_sender: Box<ScriptChan+Send>,
-    worker: TrustedWorkerAddress,
 }
 
 impl DedicatedWorkerGlobalScope {
     fn new_inherited(worker_url: Url,
-                         worker: TrustedWorkerAddress,
                          cx: Rc<Cx>,
                          resource_task: ResourceTask,
-                         parent_sender: ScriptChan,
+                         parent_sender: Box<ScriptChan+Send>,
-                         own_sender: ScriptChan,
+                         own_sender: Sender<(TrustedWorkerAddress, ScriptMsg)>,
-                         receiver: Receiver<ScriptMsg>)
+                         receiver: Receiver<(TrustedWorkerAddress, ScriptMsg)>)
                          -> DedicatedWorkerGlobalScope {
         DedicatedWorkerGlobalScope {
             workerglobalscope: WorkerGlobalScope::new_inherited(
-                WorkerGlobalScopeTypeId::DedicatedGlobalScope, worker_url, cx,
+                WorkerGlobalScopeTypeId::DedicatedGlobalScope, worker_url, cx, resource_task),
-                resource_task, own_sender),
             receiver: receiver,
+            own_sender: own_sender,
             parent_sender: parent_sender,
-            worker: worker,
+            worker: DOMRefCell::new(None),
         }
     }
 
     pub fn new(worker_url: Url,
-               worker: TrustedWorkerAddress,
                cx: Rc<Cx>,
                resource_task: ResourceTask,
-               parent_sender: ScriptChan,
+               parent_sender: Box<ScriptChan+Send>,
-               own_sender: ScriptChan,
+               own_sender: Sender<(TrustedWorkerAddress, ScriptMsg)>,
-               receiver: Receiver<ScriptMsg>)
+               receiver: Receiver<(TrustedWorkerAddress, ScriptMsg)>)
                -> Temporary<DedicatedWorkerGlobalScope> {
         let scope = box DedicatedWorkerGlobalScope::new_inherited(
-            worker_url, worker, cx.clone(), resource_task, parent_sender,
+            worker_url, cx.clone(), resource_task, parent_sender,
             own_sender, receiver);
         DedicatedWorkerGlobalScopeBinding::Wrap(cx.ptr, scope)
     }
@@ -82,9 +132,9 @@ impl DedicatedWorkerGlobalScope {
     pub fn run_worker_scope(worker_url: Url,
                             worker: TrustedWorkerAddress,
                             resource_task: ResourceTask,
-                            parent_sender: ScriptChan,
+                            parent_sender: Box<ScriptChan+Send>,
-                            own_sender: ScriptChan,
+                            own_sender: Sender<(TrustedWorkerAddress, ScriptMsg)>,
-                            receiver: Receiver<ScriptMsg>) {
+                            receiver: Receiver<(TrustedWorkerAddress, ScriptMsg)>) {
         spawn_named_native(format!("WebWorker for {}", worker_url.serialize()), proc() {
 
             task_state::initialize(SCRIPT | IN_WORKER);
@@ -104,44 +154,25 @@ impl DedicatedWorkerGlobalScope {
 
             let (_js_runtime, js_context) = ScriptTask::new_rt_and_cx();
             let global = DedicatedWorkerGlobalScope::new(
-                worker_url, worker, js_context.clone(), resource_task,
+                worker_url, js_context.clone(), resource_task,
                 parent_sender, own_sender, receiver).root();
-            match js_context.evaluate_script(
+
-                global.reflector().get_jsobject(), source, url.serialize(), 1) {
+            {
-                Ok(_) => (),
+                let _ar = AutoWorkerReset::new(*global, worker);
-                Err(_) => println!("evaluate_script failed")
+
+                match js_context.evaluate_script(
+                    global.reflector().get_jsobject(), source, url.serialize(), 1) {
+                    Ok(_) => (),
+                    Err(_) => println!("evaluate_script failed")
+                }
             }
 
-            let scope: JSRef<WorkerGlobalScope> =
-                WorkerGlobalScopeCast::from_ref(*global);
-            let target: JSRef<EventTarget> =
-                EventTargetCast::from_ref(*global);
             loop {
                 match global.receiver.recv_opt() {
-                    Ok(ScriptMsg::DOMMessage(_addr, data, nbytes)) => {
+                    Ok((linked_worker, msg)) => {
-                        let mut message = UndefinedValue();
+                        let _ar = AutoWorkerReset::new(*global, linked_worker);
-                        unsafe {
+                        global.handle_event(msg);
-                            assert!(JS_ReadStructuredClone(
-                                js_context.ptr, data as *const u64, nbytes,
-                                JS_STRUCTURED_CLONE_VERSION, &mut message,
-                                ptr::null(), ptr::null_mut()) != 0);
-                        }
-
-                        MessageEvent::dispatch_jsval(target, GlobalRef::Worker(scope), message);
-                    },
-                    Ok(ScriptMsg::RunnableMsg(runnable)) => {
-                        runnable.handler()
-                    },
-                    Ok(ScriptMsg::WorkerPostMessage(addr, data, nbytes)) => {
-                        Worker::handle_message(addr, data, nbytes);
-                    },
-                    Ok(ScriptMsg::RefcountCleanup(addr)) => {
-                        LiveDOMReferences::cleanup(js_context.ptr, addr);
                     }
-                    Ok(ScriptMsg::FireTimer(TimerSource::FromWorker, timer_id)) => {
-                        scope.handle_fire_timer(timer_id);
-                    }
-                    Ok(_) => panic!("Unexpected message"),
                     Err(_) => break,
                 }
             }
@@ -149,6 +180,58 @@ impl DedicatedWorkerGlobalScope {
     }
 }
 
+pub trait DedicatedWorkerGlobalScopeHelpers {
+    fn script_chan(self) -> Box<ScriptChan+Send>;
+}
+
+impl<'a> DedicatedWorkerGlobalScopeHelpers for JSRef<'a, DedicatedWorkerGlobalScope> {
+    fn script_chan(self) -> Box<ScriptChan+Send> {
+        box SendableWorkerScriptChan {
+            sender: self.own_sender.clone(),
+            worker: self.worker.borrow().as_ref().unwrap().clone(),
+        }
+    }
+}
+
+trait PrivateDedicatedWorkerGlobalScopeHelpers {
+    fn handle_event(self, msg: ScriptMsg);
+}
+
+impl<'a> PrivateDedicatedWorkerGlobalScopeHelpers for JSRef<'a, DedicatedWorkerGlobalScope> {
+    fn handle_event(self, msg: ScriptMsg) {
+        match msg {
+            ScriptMsg::DOMMessage(data, nbytes) => {
+                let mut message = UndefinedValue();
+                let scope: JSRef<WorkerGlobalScope> = WorkerGlobalScopeCast::from_ref(self);
+                unsafe {
+                    assert!(JS_ReadStructuredClone(
+                        scope.get_cx(), data as *const u64, nbytes,
+                        JS_STRUCTURED_CLONE_VERSION, &mut message,
+                        ptr::null(), ptr::null_mut()) != 0);
+                }
+
+                let target: JSRef<EventTarget> = EventTargetCast::from_ref(self);
+                MessageEvent::dispatch_jsval(target, GlobalRef::Worker(scope), message);
+            },
+            ScriptMsg::RunnableMsg(runnable) => {
+                runnable.handler()
+            },
+            ScriptMsg::WorkerPostMessage(addr, data, nbytes) => {
+                Worker::handle_message(addr, data, nbytes);
+            },
+            ScriptMsg::RefcountCleanup(addr) => {
+                let scope: JSRef<WorkerGlobalScope> = WorkerGlobalScopeCast::from_ref(self);
+                LiveDOMReferences::cleanup(scope.get_cx(), addr);
+            }
+            ScriptMsg::FireTimer(TimerSource::FromWorker, timer_id) => {
+                let scope: JSRef<WorkerGlobalScope> = WorkerGlobalScopeCast::from_ref(self);
+                scope.handle_fire_timer(timer_id);
+            }
+            _ => panic!("Unexpected message"),
+        }
+    }
+}
+
 impl<'a> DedicatedWorkerGlobalScopeMethods for JSRef<'a, DedicatedWorkerGlobalScope> {
     fn PostMessage(self, cx: *mut JSContext, message: JSVal) -> ErrorResult {
         let mut data = ptr::null_mut();
@@ -162,8 +245,8 @@ impl<'a> DedicatedWorkerGlobalScopeMethods for JSRef<'a, DedicatedWorkerGlobalSc
             return Err(DataClone);
         }
 
-        let ScriptChan(ref sender) = self.parent_sender;
+        let worker = self.worker.borrow().as_ref().unwrap().clone();
-        sender.send(ScriptMsg::WorkerPostMessage(self.worker.clone(), data, nbytes));
+        self.parent_sender.send(ScriptMsg::WorkerPostMessage(worker, data, nbytes));
         Ok(())
     }
 

components/script/dom/htmlformelement.rs

@@ -204,8 +204,7 @@ impl<'a> HTMLFormElementHelpers for JSRef<'a, HTMLFormElement> {
         }
 
         // This is wrong. https://html.spec.whatwg.org/multipage/forms.html#planned-navigation
-        let ScriptChan(ref script_chan) = *win.script_chan();
+        win.script_chan().send(ScriptMsg::TriggerLoad(win.page().id, load_data));
-        script_chan.send(ScriptMsg::TriggerLoad(win.page().id, load_data));
     }
 
     fn get_form_dataset<'b>(self, submitter: Option<FormSubmitter<'b>>) -> Vec<FormDatum> {

components/script/dom/window.rs

@@ -52,7 +52,7 @@ use time;
 #[dom_struct]
 pub struct Window {
     eventtarget: EventTarget,
-    script_chan: ScriptChan,
+    script_chan: Box<ScriptChan+Send>,
     control_chan: ScriptControlChan,
     console: MutNullableJS<Console>,
     location: MutNullableJS<Location>,
@@ -75,8 +75,8 @@ impl Window {
         (*js_info.as_ref().unwrap().js_context).ptr
     }
 
-    pub fn script_chan<'a>(&'a self) -> &'a ScriptChan {
+    pub fn script_chan(&self) -> Box<ScriptChan+Send> {
-        &self.script_chan
+        self.script_chan.clone()
     }
 
     pub fn control_chan<'a>(&'a self) -> &'a ScriptControlChan {
@@ -189,8 +189,7 @@ impl<'a> WindowMethods for JSRef<'a, Window> {
     }
 
     fn Close(self) {
-        let ScriptChan(ref chan) = self.script_chan;
+        self.script_chan.send(ScriptMsg::ExitWindow(self.page.id.clone()));
-        chan.send(ScriptMsg::ExitWindow(self.page.id.clone()));
     }
 
     fn Document(self) -> Temporary<Document> {
@@ -342,11 +341,10 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
         let url = UrlParser::new().base_url(&base_url).parse(href.as_slice());
         // FIXME: handle URL parse errors more gracefully.
         let url = url.unwrap();
-        let ScriptChan(ref script_chan) = self.script_chan;
         if href.as_slice().starts_with("#") {
-            script_chan.send(ScriptMsg::TriggerFragment(self.page.id, url));
+            self.script_chan.send(ScriptMsg::TriggerFragment(self.page.id, url));
         } else {
-            script_chan.send(ScriptMsg::TriggerLoad(self.page.id, LoadData::new(url)));
+            self.script_chan.send(ScriptMsg::TriggerLoad(self.page.id, LoadData::new(url)));
         }
     }
 
@@ -359,7 +357,7 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
 impl Window {
     pub fn new(cx: *mut JSContext,
                page: Rc<Page>,
-               script_chan: ScriptChan,
+               script_chan: Box<ScriptChan+Send>,
                control_chan: ScriptControlChan,
                compositor: Box<ScriptListener+'static>,
                image_cache_task: ImageCacheTask)

components/script/dom/worker.rs

@@ -39,11 +39,11 @@ pub struct Worker {
     global: GlobalField,
     /// Sender to the Receiver associated with the DedicatedWorkerGlobalScope
     /// this Worker created.
-    sender: ScriptChan,
+    sender: Sender<(TrustedWorkerAddress, ScriptMsg)>,
 }
 
 impl Worker {
-    fn new_inherited(global: &GlobalRef, sender: ScriptChan) -> Worker {
+    fn new_inherited(global: &GlobalRef, sender: Sender<(TrustedWorkerAddress, ScriptMsg)>) -> Worker {
         Worker {
             eventtarget: EventTarget::new_inherited(EventTargetTypeId::Worker),
             refcount: Cell::new(0),
@@ -52,7 +52,7 @@ impl Worker {
         }
     }
 
-    pub fn new(global: &GlobalRef, sender: ScriptChan) -> Temporary<Worker> {
+    pub fn new(global: &GlobalRef, sender: Sender<(TrustedWorkerAddress, ScriptMsg)>) -> Temporary<Worker> {
         reflect_dom_object(box Worker::new_inherited(global, sender),
                            *global,
                            WorkerBinding::Wrap)
@@ -68,13 +68,13 @@ impl Worker {
         };
 
         let resource_task = global.resource_task();
-        let (receiver, sender) = ScriptChan::new();
 
+        let (sender, receiver) = channel();
         let worker = Worker::new(global, sender.clone()).root();
-        let worker_ref = Trusted::new(global.get_cx(), *worker, global.script_chan().clone());
+        let worker_ref = Trusted::new(global.get_cx(), *worker, global.script_chan());
 
         DedicatedWorkerGlobalScope::run_worker_scope(
-            worker_url, worker_ref, resource_task, global.script_chan().clone(),
+            worker_url, worker_ref, resource_task, global.script_chan(),
             sender, receiver);
 
         Ok(Temporary::from_rooted(*worker))
@@ -112,9 +112,8 @@ impl<'a> WorkerMethods for JSRef<'a, Worker> {
             return Err(DataClone);
         }
 
-        let addr = Trusted::new(cx, self, self.global.root().root_ref().script_chan().clone());
+        let address = Trusted::new(cx, self, self.global.root().root_ref().script_chan().clone());
-        let ScriptChan(ref sender) = self.sender;
+        self.sender.send((address, ScriptMsg::DOMMessage(data, nbytes)));
-        sender.send(ScriptMsg::DOMMessage(addr, data, nbytes));
         Ok(())
     }
 

components/script/dom/workerglobalscope.rs

@@ -2,14 +2,16 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::bindings::codegen::Bindings::WorkerGlobalScopeBinding::WorkerGlobalScopeMethods;
 use dom::bindings::codegen::Bindings::FunctionBinding::Function;
+use dom::bindings::codegen::Bindings::WorkerGlobalScopeBinding::WorkerGlobalScopeMethods;
+use dom::bindings::codegen::InheritTypes::DedicatedWorkerGlobalScopeCast;
 use dom::bindings::error::{ErrorResult, Fallible};
 use dom::bindings::error::Error::{Syntax, Network, FailureUnknown};
 use dom::bindings::global::GlobalRef;
 use dom::bindings::js::{MutNullableJS, JSRef, Temporary};
 use dom::bindings::utils::Reflectable;
 use dom::console::Console;
+use dom::dedicatedworkerglobalscope::{DedicatedWorkerGlobalScope, DedicatedWorkerGlobalScopeHelpers};
 use dom::eventtarget::{EventTarget, EventTargetTypeId};
 use dom::workerlocation::WorkerLocation;
 use dom::workernavigator::WorkerNavigator;
@@ -40,7 +42,6 @@ pub struct WorkerGlobalScope {
     worker_url: Url,
     js_context: Rc<Cx>,
     resource_task: ResourceTask,
-    script_chan: ScriptChan,
     location: MutNullableJS<WorkerLocation>,
     navigator: MutNullableJS<WorkerNavigator>,
     console: MutNullableJS<Console>,
@@ -51,18 +52,16 @@ impl WorkerGlobalScope {
     pub fn new_inherited(type_id: WorkerGlobalScopeTypeId,
                          worker_url: Url,
                          cx: Rc<Cx>,
-                         resource_task: ResourceTask,
+                         resource_task: ResourceTask) -> WorkerGlobalScope {
-                         script_chan: ScriptChan) -> WorkerGlobalScope {
         WorkerGlobalScope {
             eventtarget: EventTarget::new_inherited(EventTargetTypeId::WorkerGlobalScope(type_id)),
             worker_url: worker_url,
             js_context: cx,
             resource_task: resource_task,
-            script_chan: script_chan,
             location: Default::default(),
             navigator: Default::default(),
             console: Default::default(),
-            timers: TimerManager::new()
+            timers: TimerManager::new(),
         }
     }
 
@@ -82,10 +81,6 @@ impl WorkerGlobalScope {
     pub fn get_url<'a>(&'a self) -> &'a Url {
         &self.worker_url
     }
-
-    pub fn script_chan<'a>(&'a self) -> &'a ScriptChan {
-        &self.script_chan
-    }
 }
 
 impl<'a> WorkerGlobalScopeMethods for JSRef<'a, WorkerGlobalScope> {
@@ -153,7 +148,7 @@ impl<'a> WorkerGlobalScopeMethods for JSRef<'a, WorkerGlobalScope> {
                                             timeout,
                                             IsInterval::NonInterval,
                                             TimerSource::FromWorker,
-                                            self.script_chan.clone())
+                                            self.script_chan())
     }
 
     fn ClearTimeout(self, handle: i32) {
@@ -166,7 +161,7 @@ impl<'a> WorkerGlobalScopeMethods for JSRef<'a, WorkerGlobalScope> {
                                             timeout,
                                             IsInterval::Interval,
                                             TimerSource::FromWorker,
-                                            self.script_chan.clone())
+                                            self.script_chan())
     }
 
     fn ClearInterval(self, handle: i32) {
@@ -176,13 +171,26 @@ impl<'a> WorkerGlobalScopeMethods for JSRef<'a, WorkerGlobalScope> {
 
 pub trait WorkerGlobalScopeHelpers {
     fn handle_fire_timer(self, timer_id: TimerId);
+    fn script_chan(self) -> Box<ScriptChan+Send>;
+    fn get_cx(self) -> *mut JSContext;
 }
 
 impl<'a> WorkerGlobalScopeHelpers for JSRef<'a, WorkerGlobalScope> {
+    fn script_chan(self) -> Box<ScriptChan+Send> {
+        let dedicated: Option<JSRef<DedicatedWorkerGlobalScope>> =
+            DedicatedWorkerGlobalScopeCast::to_ref(self);
+        match dedicated {
+            Some(dedicated) => dedicated.script_chan(),
+            None => panic!("need to implement a sender for SharedWorker"),
+        }
+    }
 
     fn handle_fire_timer(self, timer_id: TimerId) {
         self.timers.fire_timer(timer_id, self);
     }
 
+    fn get_cx(self) -> *mut JSContext {
+        self.js_context.ptr
+    }
 }
 

components/script/dom/xmlhttprequest.rs

@@ -117,7 +117,7 @@ impl XHRProgress {
 
 enum SyncOrAsync<'a> {
     Sync(JSRef<'a, XMLHttpRequest>),
-    Async(TrustedXHRAddress, &'a ScriptChan)
+    Async(TrustedXHRAddress, Box<ScriptChan+Send>)
 }
 
 enum TerminateReason {
@@ -214,9 +214,8 @@ impl XMLHttpRequest {
                 SyncOrAsync::Sync(xhr) => {
                     xhr.process_partial_response(msg);
                 },
-                SyncOrAsync::Async(ref addr, script_chan) => {
+                SyncOrAsync::Async(ref addr, ref script_chan) => {
-                    let ScriptChan(ref chan) = *script_chan;
+                    script_chan.send(ScriptMsg::RunnableMsg(box XHRProgressHandler::new(addr.clone(), msg)));
-                    chan.send(ScriptMsg::RunnableMsg(box XHRProgressHandler::new(addr.clone(), msg)));
                 }
             }
         }
@@ -614,16 +613,14 @@ impl<'a> XMLHttpRequestMethods for JSRef<'a, XMLHttpRequest> {
                                          terminate_receiver, cors_request, gen_id, start_port);
         } else {
             self.fetch_time.set(time::now().to_timespec().sec);
-            let script_chan = global.root_ref().script_chan().clone();
+            let script_chan = global.root_ref().script_chan();
-            // Pin the object before launching the fetch task.
+            // Pin the object before launching the fetch task. This is to ensure that
-            // The `ScriptMsg::RunnableMsg` sent when the fetch task completes will
+            // the object will stay alive as long as there are (possibly cancelled)
-            // unpin it. This is to ensure that the object will stay alive
+            // inflight events queued up in the script task's port.
-            // as long as there are (possibly cancelled) inflight events queued up
-            // in the script task's port
             let addr = Trusted::new(self.global.root().root_ref().get_cx(), self,
                                     script_chan.clone());
             spawn_named("XHRTask", proc() {
-                let _ = XMLHttpRequest::fetch(&mut SyncOrAsync::Async(addr, &script_chan),
+                let _ = XMLHttpRequest::fetch(&mut SyncOrAsync::Async(addr, script_chan),
                                               resource_task,
                                               load_data,
                                               terminate_receiver,

components/script/script_task.rs

@@ -64,7 +64,7 @@ use geom::point::Point2D;
 use hyper::header::{Header, HeaderFormat};
 use hyper::header::common::util as header_util;
 use js::jsapi::{JS_SetWrapObjectCallbacks, JS_SetGCZeal, JS_DEFAULT_ZEAL_FREQ, JS_GC};
-use js::jsapi::{JSContext, JSRuntime, JSTracer};
+use js::jsapi::{JSContext, JSRuntime};
 use js::jsapi::{JS_SetGCParameter, JSGC_MAX_BYTES};
 use js::jsapi::{JS_SetGCCallback, JSGCStatus, JSGC_BEGIN, JSGC_END};
 use js::rust::{Cx, RtUtils};
@@ -113,7 +113,7 @@ pub enum ScriptMsg {
     ExitWindow(PipelineId),
     /// Message sent through Worker.postMessage (only dispatched to
     /// DedicatedWorkerGlobalScope).
-    DOMMessage(TrustedWorkerAddress, *mut u64, size_t),
+    DOMMessage(*mut u64, size_t),
     /// Posts a message to the Worker object (dispatched to all tasks).
     WorkerPostMessage(TrustedWorkerAddress, *mut u64, size_t),
     /// Generic message that encapsulates event handling.
@@ -122,17 +122,35 @@ pub enum ScriptMsg {
     RefcountCleanup(*const libc::c_void),
 }
 
+/// A cloneable interface for communicating with an event loop.
+pub trait ScriptChan {
+    /// Send a message to the associated event loop.
+    fn send(&self, msg: ScriptMsg);
+    /// Clone this handle.
+    fn clone(&self) -> Box<ScriptChan+Send>;
+}
+
 /// Encapsulates internal communication within the script task.
-#[deriving(Clone)]
+#[jstraceable]
-pub struct ScriptChan(pub Sender<ScriptMsg>);
+pub struct NonWorkerScriptChan(pub Sender<ScriptMsg>);
 
-no_jsmanaged_fields!(ScriptChan)
+impl ScriptChan for NonWorkerScriptChan {
+    fn send(&self, msg: ScriptMsg) {
+        let NonWorkerScriptChan(ref chan) = *self;
+        chan.send(msg);
+    }
 
-impl ScriptChan {
+    fn clone(&self) -> Box<ScriptChan+Send> {
+        let NonWorkerScriptChan(ref chan) = *self;
+        box NonWorkerScriptChan(chan.clone())
+    }
+}
+
+impl NonWorkerScriptChan {
     /// Creates a new script chan.
-    pub fn new() -> (Receiver<ScriptMsg>, ScriptChan) {
+    pub fn new() -> (Receiver<ScriptMsg>, Box<NonWorkerScriptChan>) {
         let (chan, port) = channel();
-        (port, ScriptChan(chan))
+        (port, box NonWorkerScriptChan(chan))
     }
 }
 
@@ -167,7 +185,7 @@ pub struct ScriptTask {
     port: Receiver<ScriptMsg>,
     /// A channel to hand out to script task-based entities that need to be able to enqueue
     /// events in the event queue.
-    chan: ScriptChan,
+    chan: NonWorkerScriptChan,
 
     /// A channel to hand out to tasks that need to respond to a message from the script task.
     control_chan: ScriptControlChan,
@@ -282,7 +300,7 @@ impl ScriptTaskFactory for ScriptTask {
                                               box compositor as Box<ScriptListener>,
                                               layout_chan,
                                               script_port,
-                                              ScriptChan(script_chan),
+                                              NonWorkerScriptChan(script_chan),
                                               control_chan,
                                               control_port,
                                               constellation_chan,
@@ -314,7 +332,7 @@ impl ScriptTask {
                compositor: Box<ScriptListener+'static>,
                layout_chan: LayoutChan,
                port: Receiver<ScriptMsg>,
-               chan: ScriptChan,
+               chan: NonWorkerScriptChan,
                control_chan: ScriptControlChan,
                control_port: Receiver<ConstellationControlMsg>,
                constellation_chan: ConstellationChan,
@@ -583,7 +601,7 @@ impl ScriptTask {
             ScriptMsg::RunnableMsg(runnable) =>
                 runnable.handler(),
             ScriptMsg::RefcountCleanup(addr) =>
-                LiveDOMReferences::cleanup(self.js_context.borrow().as_ref().unwrap().ptr, addr),
+                LiveDOMReferences::cleanup(self.get_cx(), addr),
         }
     }
 

components/script/timers.rs

@@ -100,7 +100,7 @@ impl TimerManager {
                                   timeout: i32,
                                   is_interval: IsInterval,
                                   source: TimerSource,
-                                  script_chan: ScriptChan)
+                                  script_chan: Box<ScriptChan+Send>)
                                   -> i32 {
         let timeout = cmp::max(0, timeout) as u64;
         let handle = self.next_timer_handle.get();
@@ -136,8 +136,7 @@ impl TimerManager {
                 let id = select.wait();
                 if id == timeout_handle.id() {
                     timeout_port.recv();
-                    let ScriptChan(ref chan) = script_chan;
+                    script_chan.send(ScriptMsg::FireTimer(source, TimerId(handle)));
-                    chan.send(ScriptMsg::FireTimer(source, TimerId(handle)));
                     if is_interval == IsInterval::NonInterval {
                         break;
                     }