introduce "per task source" ignoring of tasks

20 files changed, 106 insertions, 34 deletions

diff --git a/components/script/Cargo.toml b/components/script/Cargo.toml
index 7f30c842d34..7b2077c5fac 100644
--- a/components/script/Cargo.toml
+++ b/components/script/Cargo.toml
@@ -44,6 +44,7 @@ dom_struct = {path = "../dom_struct"}
 domobject_derive = {path = "../domobject_derive"}
 embedder_traits = {path = "../embedder_traits"}
 encoding_rs = "0.7"
+enum-iterator = "0.2.0"
 euclid = "0.17"
 fnv = "1.0"
 gleam = "0.5"
diff --git a/components/script/dom/eventsource.rs b/components/script/dom/eventsource.rs
index 3f2b829a457..f0b5726e6a3 100644
--- a/components/script/dom/eventsource.rs
+++ b/components/script/dom/eventsource.rs
@@ -34,7 +34,7 @@ use std::cell::Cell;
 use std::mem;
 use std::str::{Chars, FromStr};
 use std::sync::{Arc, Mutex};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 use timers::OneshotTimerCallback;
 use utf8;
 
@@ -482,10 +482,12 @@ impl EventSource {
             data: String::new(),
             last_event_id: String::new(),
         };
+        // TODO: use the "remote event task source", and canceller.
+        // https://html.spec.whatwg.org/multipage/#remote-event-task-source
         let listener = NetworkListener {
             context: Arc::new(Mutex::new(context)),
             task_source: global.networking_task_source(),
-            canceller: Some(global.task_canceller())
+            canceller: Some(global.task_canceller(TaskSourceName::Networking))
         };
         ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
             listener.notify_fetch(message.to().unwrap());
diff --git a/components/script/dom/filereader.rs b/components/script/dom/filereader.rs
index 037e54907c0..6b88c645bbd 100644
--- a/components/script/dom/filereader.rs
+++ b/components/script/dom/filereader.rs
@@ -35,7 +35,7 @@ use std::ptr;
 use std::sync::Arc;
 use std::thread;
 use task::TaskCanceller;
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 use task_source::file_reading::{FileReadingTask, FileReadingTaskSource};
 
 #[derive(Clone, Copy, JSTraceable, MallocSizeOf, PartialEq)]
@@ -452,7 +452,7 @@ impl FileReader {
         let gen_id = self.generation_id.get();
 
         let global = self.global();
-        let canceller = global.task_canceller();
+        let canceller = global.task_canceller(TaskSourceName::FileReading);
         let task_source = global.file_reading_task_source();
 
         thread::Builder::new()
diff --git a/components/script/dom/globalscope.rs b/components/script/dom/globalscope.rs
index cec59c92510..759216df27a 100644
--- a/components/script/dom/globalscope.rs
+++ b/components/script/dom/globalscope.rs
@@ -52,6 +52,7 @@ use std::rc::Rc;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
 use task::TaskCanceller;
+use task_source::TaskSourceName;
 use task_source::file_reading::FileReadingTaskSource;
 use task_source::networking::NetworkingTaskSource;
 use task_source::performance_timeline::PerformanceTimelineTaskSource;
@@ -508,11 +509,14 @@ impl GlobalScope {
 
     /// Returns the task canceller of this global to ensure that everything is
     /// properly cancelled when the global scope is destroyed.
-    pub fn task_canceller(&self) -> TaskCanceller {
+    pub fn task_canceller(&self, name: TaskSourceName) -> TaskCanceller {
         if let Some(window) = self.downcast::<Window>() {
-            return window.task_canceller();
+            return window.task_canceller(name);
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
+            // Note: the "name" is not passed to the worker,
+            // because 'closing' it only requires one task canceller for all task sources.
+            // https://html.spec.whatwg.org/multipage/#dom-workerglobalscope-closing
             return worker.task_canceller();
         }
         unreachable!();
diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index b37199ca0db..668c66d7734 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -58,7 +58,7 @@ use std::i32;
 use std::sync::{Arc, Mutex};
 use style::attr::{AttrValue, LengthOrPercentageOrAuto, parse_double, parse_unsigned_integer};
 use style::str::is_ascii_digit;
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 
 enum ParseState {
     InDescriptor,
@@ -185,7 +185,7 @@ impl HTMLImageElement {
 
             let window = window_from_node(elem);
             let task_source = window.networking_task_source();
-            let task_canceller = window.task_canceller();
+            let task_canceller = window.task_canceller(TaskSourceName::Networking);
             let generation = elem.generation.get();
             ROUTER.add_route(responder_receiver.to_opaque(), Box::new(move |message| {
                 debug!("Got image {:?}", message);
@@ -253,7 +253,7 @@ impl HTMLImageElement {
         let listener = NetworkListener {
             context: context,
             task_source: window.networking_task_source(),
-            canceller: Some(window.task_canceller()),
+            canceller: Some(window.task_canceller(TaskSourceName::Networking)),
         };
         ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
             listener.notify_fetch(message.to().unwrap());
diff --git a/components/script/dom/htmlmediaelement.rs b/components/script/dom/htmlmediaelement.rs
index 1122e267e7e..466bcae3280 100644
--- a/components/script/dom/htmlmediaelement.rs
+++ b/components/script/dom/htmlmediaelement.rs
@@ -46,7 +46,7 @@ use std::collections::VecDeque;
 use std::mem;
 use std::rc::Rc;
 use std::sync::{Arc, Mutex};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 use time::{self, Timespec, Duration};
 
 #[dom_struct]
@@ -608,7 +608,7 @@ impl HTMLMediaElement {
                 let listener = NetworkListener {
                     context: context,
                     task_source: window.networking_task_source(),
-                    canceller: Some(window.task_canceller())
+                    canceller: Some(window.task_canceller(TaskSourceName::Networking))
                 };
                 ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
                     listener.notify_fetch(message.to().unwrap());
diff --git a/components/script/dom/htmlscriptelement.rs b/components/script/dom/htmlscriptelement.rs
index ee42746c71f..8f07f1e80c8 100644
--- a/components/script/dom/htmlscriptelement.rs
+++ b/components/script/dom/htmlscriptelement.rs
@@ -41,6 +41,7 @@ use std::path::PathBuf;
 use std::process::{Command, Stdio};
 use std::sync::{Arc, Mutex};
 use style::str::{HTML_SPACE_CHARACTERS, StaticStringVec};
+use task_source::TaskSourceName;
 use uuid::Uuid;
 
 #[dom_struct]
@@ -273,7 +274,7 @@ fn fetch_a_classic_script(script: &HTMLScriptElement,
     let listener = NetworkListener {
         context: context,
         task_source: doc.window().networking_task_source(),
-        canceller: Some(doc.window().task_canceller())
+        canceller: Some(doc.window().task_canceller(TaskSourceName::Networking))
     };
 
     ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
diff --git a/components/script/dom/websocket.rs b/components/script/dom/websocket.rs
index 031741db0df..14ff325f56d 100644
--- a/components/script/dom/websocket.rs
+++ b/components/script/dom/websocket.rs
@@ -39,7 +39,7 @@ use std::cell::Cell;
 use std::ptr;
 use std::thread;
 use task::{TaskOnce, TaskCanceller};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 use task_source::networking::NetworkingTaskSource;
 
 #[derive(Clone, Copy, Debug, JSTraceable, MallocSizeOf, PartialEq)]
@@ -199,8 +199,11 @@ impl WebSocket {
         };
         let _ = global.core_resource_thread().send(CoreResourceMsg::Fetch(request, channels));
 
+        // TODO: use a dedicated task source,
+        // https://html.spec.whatwg.org/multipage/#websocket-task-source
+        // When making the switch, also update the task_canceller call.
         let task_source = global.networking_task_source();
-        let canceller = global.task_canceller();
+        let canceller = global.task_canceller(TaskSourceName::Networking);
         thread::spawn(move || {
             while let Ok(event) = dom_event_receiver.recv() {
                 match event {
@@ -391,8 +394,13 @@ impl WebSocketMethods for WebSocket {
                 self.ready_state.set(WebSocketRequestState::Closing);
 
                 let address = Trusted::new(self);
+                // TODO: use a dedicated task source,
+                // https://html.spec.whatwg.org/multipage/#websocket-task-source
+                // When making the switch, also update the task_canceller call.
                 let task_source = self.global().networking_task_source();
-                fail_the_websocket_connection(address, &task_source, &self.global().task_canceller());
+                fail_the_websocket_connection(address,
+                                              &task_source,
+                                              &self.global().task_canceller(TaskSourceName::Networking));
             }
             WebSocketRequestState::Open => {
                 self.ready_state.set(WebSocketRequestState::Closing);
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index b536f28345f..d0d6e499639 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -109,6 +109,7 @@ use style::str::HTML_SPACE_CHARACTERS;
 use style::stylesheets::CssRuleType;
 use style_traits::{CSSPixel, DevicePixel, ParsingMode};
 use task::TaskCanceller;
+use task_source::TaskSourceName;
 use task_source::dom_manipulation::DOMManipulationTaskSource;
 use task_source::file_reading::FileReadingTaskSource;
 use task_source::history_traversal::HistoryTraversalTaskSource;
@@ -246,9 +247,9 @@ pub struct Window {
 
     current_viewport: Cell<Rect<Au>>,
 
-    /// A flag to prevent async events from attempting to interact with this window.
+    /// A map of flags to prevent events from a given task source from attempting to interact with this window.
     #[ignore_malloc_size_of = "defined in std"]
-    ignore_further_async_events: DomRefCell<Arc<AtomicBool>>,
+    ignore_further_async_events: DomRefCell<HashMap<TaskSourceName, Arc<AtomicBool>>>,
 
     error_reporter: CSSErrorReporter,
 
@@ -308,7 +309,15 @@ impl Window {
             *self.js_runtime.borrow_for_script_deallocation() = None;
             self.window_proxy.set(None);
             self.current_state.set(WindowState::Zombie);
-            self.ignore_further_async_events.borrow().store(true, Ordering::Relaxed);
+            self.ignore_all_events();
+        }
+    }
+
+    fn ignore_all_events(&self) {
+        let mut ignore_flags = self.ignore_further_async_events.borrow_mut();
+        for task_source_name in TaskSourceName::all() {
+            let flag = ignore_flags.entry(task_source_name).or_insert(Default::default());
+            flag.store(true, Ordering::Relaxed);
         }
     }
 
@@ -1065,9 +1074,11 @@ impl Window {
         self.paint_worklet.or_init(|| self.new_paint_worklet())
     }
 
-    pub fn task_canceller(&self) -> TaskCanceller {
+    pub fn task_canceller(&self, name: TaskSourceName) -> TaskCanceller {
+        let mut flags = self.ignore_further_async_events.borrow_mut();
+        let cancel_flag = flags.entry(name).or_insert(Default::default());
         TaskCanceller {
-            cancelled: Some(self.ignore_further_async_events.borrow().clone()),
+            cancelled: Some(cancel_flag.clone()),
         }
     }
 
@@ -1084,8 +1095,12 @@ impl Window {
     /// This sets the current `ignore_further_async_events` sentinel value to
     /// `true` and replaces it with a brand new one for future tasks.
     pub fn cancel_all_tasks(&self) {
-        let cancelled = mem::replace(&mut *self.ignore_further_async_events.borrow_mut(), Default::default());
-        cancelled.store(true, Ordering::Relaxed);
+        let mut ignore_flags = self.ignore_further_async_events.borrow_mut();
+        for task_source_name in TaskSourceName::all() {
+            let mut flag = ignore_flags.entry(task_source_name).or_insert(Default::default());
+            let cancelled = mem::replace(&mut *flag, Default::default());
+            cancelled.store(true, Ordering::Relaxed);
+        }
     }
 
     pub fn clear_js_runtime(&self) {
@@ -1117,7 +1132,7 @@ impl Window {
         self.current_state.set(WindowState::Zombie);
         *self.js_runtime.borrow_mut() = None;
         self.window_proxy.set(None);
-        self.ignore_further_async_events.borrow().store(true, Ordering::SeqCst);
+        self.ignore_all_events();
     }
 
     /// <https://drafts.csswg.org/cssom-view/#dom-window-scroll>
@@ -1998,9 +2013,10 @@ impl Window {
         });
         // FIXME(nox): Why are errors silenced here?
         // TODO(#12718): Use the "posted message task source".
+        // TODO: When switching to the right task source, update the task_canceller call too.
         let _ = self.script_chan.send(CommonScriptMsg::Task(
             ScriptThreadEventCategory::DomEvent,
-            Box::new(self.task_canceller().wrap_task(task)),
+            Box::new(self.task_canceller(TaskSourceName::DOMManipulation).wrap_task(task)),
             self.pipeline_id()
         ));
     }
diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index 49a72bbf46d..3dee1e18fe6 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -70,6 +70,7 @@ use std::ptr::NonNull;
 use std::slice;
 use std::str;
 use std::sync::{Arc, Mutex};
+use task_source::TaskSourceName;
 use task_source::networking::NetworkingTaskSource;
 use time;
 use timers::{OneshotTimerCallback, OneshotTimerHandle};
@@ -268,7 +269,7 @@ impl XMLHttpRequest {
         let listener = NetworkListener {
             context: context,
             task_source: task_source,
-            canceller: Some(global.task_canceller())
+            canceller: Some(global.task_canceller(TaskSourceName::Networking))
         };
         ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
             listener.notify_fetch(message.to().unwrap());
diff --git a/components/script/fetch.rs b/components/script/fetch.rs
index d7a688ced94..7f866ca8633 100644
--- a/components/script/fetch.rs
+++ b/components/script/fetch.rs
@@ -31,6 +31,7 @@ use servo_url::ServoUrl;
 use std::mem;
 use std::rc::Rc;
 use std::sync::{Arc, Mutex};
+use task_source::TaskSourceName;
 
 struct FetchContext {
     fetch_promise: Option<TrustedPromise>,
@@ -154,7 +155,7 @@ pub fn Fetch(global: &GlobalScope, input: RequestInfo, init: RootedTraceableBox<
     let listener = NetworkListener {
         context: fetch_context,
         task_source: global.networking_task_source(),
-        canceller: Some(global.task_canceller())
+        canceller: Some(global.task_canceller(TaskSourceName::Networking))
     };
 
     ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
diff --git a/components/script/layout_image.rs b/components/script/layout_image.rs
index 6cbdd292fe1..553972d24b1 100644
--- a/components/script/layout_image.rs
+++ b/components/script/layout_image.rs
@@ -17,6 +17,7 @@ use net_traits::request::{Destination, RequestInit as FetchRequestInit};
 use network_listener::{NetworkListener, PreInvoke};
 use servo_url::ServoUrl;
 use std::sync::{Arc, Mutex};
+use task_source::TaskSourceName;
 
 struct LayoutImageContext {
     id: PendingImageId,
@@ -62,7 +63,7 @@ pub fn fetch_image_for_layout(url: ServoUrl,
     let listener = NetworkListener {
         context: context,
         task_source: window.networking_task_source(),
-        canceller: Some(window.task_canceller()),
+        canceller: Some(window.task_canceller(TaskSourceName::Networking)),
     };
     ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
         listener.notify_fetch(message.to().unwrap());
diff --git a/components/script/lib.rs b/components/script/lib.rs
index cf020ab9ac6..837b744424c 100644
--- a/components/script/lib.rs
+++ b/components/script/lib.rs
@@ -37,6 +37,7 @@ extern crate dom_struct;
 extern crate domobject_derive;
 extern crate embedder_traits;
 extern crate encoding_rs;
+#[macro_use] extern crate enum_iterator;
 extern crate euclid;
 extern crate fnv;
 extern crate gleam;
diff --git a/components/script/stylesheet_loader.rs b/components/script/stylesheet_loader.rs
index 0c5e792ad6a..156d2577656 100644
--- a/components/script/stylesheet_loader.rs
+++ b/components/script/stylesheet_loader.rs
@@ -35,6 +35,7 @@ use style::stylesheets::{CssRules, ImportRule, Namespaces, Stylesheet, Styleshee
 use style::stylesheets::StylesheetLoader as StyleStylesheetLoader;
 use style::stylesheets::import_rule::ImportSheet;
 use style::values::CssUrl;
+use task_source::TaskSourceName;
 
 pub trait StylesheetOwner {
     /// Returns whether this element was inserted by the parser (i.e., it should
@@ -228,7 +229,7 @@ impl<'a> StylesheetLoader<'a> {
         let listener = NetworkListener {
             context: context,
             task_source: document.window().networking_task_source(),
-            canceller: Some(document.window().task_canceller())
+            canceller: Some(document.window().task_canceller(TaskSourceName::Networking))
         };
         ROUTER.add_route(action_receiver.to_opaque(), Box::new(move |message| {
             listener.notify_fetch(message.to().unwrap());
diff --git a/components/script/task_source/dom_manipulation.rs b/components/script/task_source/dom_manipulation.rs
index 5b5e55570b4..03b2d85a945 100644
--- a/components/script/task_source/dom_manipulation.rs
+++ b/components/script/task_source/dom_manipulation.rs
@@ -15,7 +15,7 @@ use std::fmt;
 use std::result::Result;
 use std::sync::mpsc::Sender;
 use task::{TaskCanceller, TaskOnce};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 
 #[derive(Clone, JSTraceable)]
 pub struct DOMManipulationTaskSource(pub Sender<MainThreadScriptMsg>, pub PipelineId);
@@ -27,6 +27,8 @@ impl fmt::Debug for DOMManipulationTaskSource {
 }
 
 impl TaskSource for DOMManipulationTaskSource {
+     const NAME: TaskSourceName = TaskSourceName::DOMManipulation;
+
     fn queue_with_canceller<T>(
         &self,
         task: T,
diff --git a/components/script/task_source/file_reading.rs b/components/script/task_source/file_reading.rs
index e94f957234c..8fd3a143eff 100644
--- a/components/script/task_source/file_reading.rs
+++ b/components/script/task_source/file_reading.rs
@@ -8,7 +8,7 @@ use msg::constellation_msg::PipelineId;
 use script_runtime::{CommonScriptMsg, ScriptThreadEventCategory, ScriptChan};
 use std::sync::Arc;
 use task::{TaskCanceller, TaskOnce};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 
 #[derive(JSTraceable)]
 pub struct FileReadingTaskSource(pub Box<ScriptChan + Send + 'static>, pub PipelineId);
@@ -20,6 +20,8 @@ impl Clone for FileReadingTaskSource {
 }
 
 impl TaskSource for FileReadingTaskSource {
+    const NAME: TaskSourceName = TaskSourceName::FileReading;
+
     fn queue_with_canceller<T>(
         &self,
         task: T,
diff --git a/components/script/task_source/mod.rs b/components/script/task_source/mod.rs
index 4818ba2c80c..cf605976b46 100644
--- a/components/script/task_source/mod.rs
+++ b/components/script/task_source/mod.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/. */
 
+
 pub mod dom_manipulation;
 pub mod file_reading;
 pub mod history_traversal;
@@ -10,10 +11,33 @@ pub mod performance_timeline;
 pub mod user_interaction;
 
 use dom::globalscope::GlobalScope;
+use enum_iterator::IntoEnumIterator;
 use std::result::Result;
 use task::{TaskCanceller, TaskOnce};
 
+// The names of all task sources, used to differentiate TaskCancellers.
+// Note: When adding a task source, update this enum.
+// Note: The HistoryTraversalTaskSource is not part of this,
+// because it doesn't implement TaskSource.
+#[derive(Eq, Hash, IntoEnumIterator, JSTraceable, PartialEq)]
+pub enum TaskSourceName {
+    DOMManipulation,
+    FileReading,
+    HistoryTraversal,
+    Networking,
+    PerformanceTimeline,
+    UserInteraction
+}
+
+impl TaskSourceName {
+    pub fn all() -> Vec<TaskSourceName> {
+        TaskSourceName::into_enum_iter().collect()
+    }
+}
+
 pub trait TaskSource {
+    const NAME: TaskSourceName;
+
     fn queue_with_canceller<T>(
         &self,
         task: T,
@@ -26,6 +50,7 @@ pub trait TaskSource {
     where
         T: TaskOnce + 'static,
     {
-        self.queue_with_canceller(task, &global.task_canceller())
+        let canceller = global.task_canceller(Self::NAME);
+        self.queue_with_canceller(task, &canceller)
     }
 }
diff --git a/components/script/task_source/networking.rs b/components/script/task_source/networking.rs
index ed192d08003..9058f9653e4 100644
--- a/components/script/task_source/networking.rs
+++ b/components/script/task_source/networking.rs
@@ -5,7 +5,7 @@
 use msg::constellation_msg::PipelineId;
 use script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory};
 use task::{TaskCanceller, TaskOnce};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 
 #[derive(JSTraceable)]
 pub struct NetworkingTaskSource(pub Box<ScriptChan + Send + 'static>, pub PipelineId);
@@ -17,6 +17,8 @@ impl Clone for NetworkingTaskSource {
 }
 
 impl TaskSource for NetworkingTaskSource {
+    const NAME: TaskSourceName = TaskSourceName::Networking;
+
     fn queue_with_canceller<T>(
         &self,
         task: T,
diff --git a/components/script/task_source/performance_timeline.rs b/components/script/task_source/performance_timeline.rs
index 9f72305b00e..05591bbe71b 100644
--- a/components/script/task_source/performance_timeline.rs
+++ b/components/script/task_source/performance_timeline.rs
@@ -13,7 +13,7 @@ use script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory};
 use std::fmt;
 use std::result::Result;
 use task::{TaskCanceller, TaskOnce};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 
 #[derive(JSTraceable)]
 pub struct PerformanceTimelineTaskSource(pub Box<ScriptChan + Send + 'static>, pub PipelineId);
@@ -31,6 +31,8 @@ impl fmt::Debug for PerformanceTimelineTaskSource {
 }
 
 impl TaskSource for PerformanceTimelineTaskSource {
+    const NAME: TaskSourceName = TaskSourceName::PerformanceTimeline;
+
     fn queue_with_canceller<T>(
         &self,
         task: T,
diff --git a/components/script/task_source/user_interaction.rs b/components/script/task_source/user_interaction.rs
index 12f822afedd..2ace44f1093 100644
--- a/components/script/task_source/user_interaction.rs
+++ b/components/script/task_source/user_interaction.rs
@@ -15,7 +15,7 @@ use std::fmt;
 use std::result::Result;
 use std::sync::mpsc::Sender;
 use task::{TaskCanceller, TaskOnce};
-use task_source::TaskSource;
+use task_source::{TaskSource, TaskSourceName};
 
 #[derive(Clone, JSTraceable)]
 pub struct UserInteractionTaskSource(pub Sender<MainThreadScriptMsg>, pub PipelineId);
@@ -27,6 +27,8 @@ impl fmt::Debug for UserInteractionTaskSource {
 }
 
 impl TaskSource for UserInteractionTaskSource {
+    const NAME: TaskSourceName = TaskSourceName::UserInteraction;
+
     fn queue_with_canceller<T>(
         &self,
         task: T,