Unify the task source and task canceller API

I moved away from the `Window` struct all the logic to handle task
sources, into a new struct called `TaskManager`. In a happy world, I'd
be able to just have there two functions, of the types:

```rust
fn task_source<T: TaskSource>(&self, name: TaskSourceName) -> Box<T>
fn task_source_with_canceller<T: TaskSource>(&self, name: TaskSourceName)
  -> (Box<T>, TaskSourceCanceller)
```

And not so much duplicated code. However, because TaskSource can't be a
trait object (because it has generic type parameters), that's not
possible. Instead, I decided to reduce duplicated logic through macros.

For reasons[1], I have to pass both the name of the function with
canceller and the name of the function without, as I'm not able to
concatenate them in the macro itself. I could probably use
`concat_idents` to create both types already defined and reduce the
amount of arguments by one, but that macro is nightly only. At the same
time, not being able to declare macros inside `impl` forces me to pass
`self` as an argument.

All this makes this solution more verbose than it would be ideally. It
does reduce duplication, but it doesn't reduce the size of the file.

[1](rust-lang/rust#29599)

components/script/dom/analysernode.rs

@@ -17,7 +17,7 @@ use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::reflect_dom_object;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::window::Window;
-use crate::task_source::{TaskSource, TaskSourceName};
+use crate::task_source::TaskSource;
 use dom_struct::dom_struct;
 use ipc_channel::ipc::{self, IpcReceiver};
 use ipc_channel::router::ROUTER;
@@ -97,8 +97,9 @@ impl AnalyserNode {
     ) -> Fallible<DomRoot<AnalyserNode>> {
         let (node, recv) = AnalyserNode::new_inherited(window, context, options)?;
         let object = reflect_dom_object(Box::new(node), window, AnalyserNodeBinding::Wrap);
-        let source = window.dom_manipulation_task_source();
-        let canceller = window.task_canceller(TaskSourceName::DOMManipulation);
+        let (source, canceller) = window
+            .task_manager()
+            .dom_manipulation_task_source_with_canceller();
         let this = Trusted::new(&*object);
 
         ROUTER.add_route(

components/script/dom/audiocontext.rs

@@ -126,7 +126,7 @@ impl AudioContextMethods for AudioContext {
 
         // Steps 4 and 5.
         let window = DomRoot::downcast::<Window>(self.global()).unwrap();
-        let task_source = window.dom_manipulation_task_source();
+        let task_source = window.task_manager().dom_manipulation_task_source();
         let trusted_promise = TrustedPromise::new(promise.clone());
         match self.context.audio_context_impl().suspend() {
             Ok(_) => {
@@ -141,7 +141,7 @@ impl AudioContextMethods for AudioContext {
                     if base_context.State() != AudioContextState::Suspended {
                         base_context.set_state_attribute(AudioContextState::Suspended);
                         let window = DomRoot::downcast::<Window>(context.global()).unwrap();
-                        window.dom_manipulation_task_source().queue_simple_event(
+                        window.task_manager().dom_manipulation_task_source().queue_simple_event(
                             context.upcast(),
                             atom!("statechange"),
                             &window
@@ -188,7 +188,7 @@ impl AudioContextMethods for AudioContext {
 
         // Steps 4 and 5.
         let window = DomRoot::downcast::<Window>(self.global()).unwrap();
-        let task_source = window.dom_manipulation_task_source();
+        let task_source = window.task_manager().dom_manipulation_task_source();
         let trusted_promise = TrustedPromise::new(promise.clone());
         match self.context.audio_context_impl().close() {
             Ok(_) => {
@@ -203,7 +203,7 @@ impl AudioContextMethods for AudioContext {
                     if base_context.State() != AudioContextState::Closed {
                         base_context.set_state_attribute(AudioContextState::Closed);
                         let window = DomRoot::downcast::<Window>(context.global()).unwrap();
-                        window.dom_manipulation_task_source().queue_simple_event(
+                        window.task_manager().dom_manipulation_task_source().queue_simple_event(
                             context.upcast(),
                             atom!("statechange"),
                             &window

components/script/dom/audioscheduledsourcenode.rs

@@ -10,7 +10,7 @@ use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::DomObject;
-use crate::task_source::{TaskSource, TaskSourceName};
+use crate::task_source::TaskSource;
 use dom_struct::dom_struct;
 use servo_media::audio::node::OnEndedCallback;
 use servo_media::audio::node::{AudioNodeInit, AudioNodeMessage, AudioScheduledSourceNodeMessage};
@@ -71,15 +71,16 @@ impl AudioScheduledSourceNodeMethods for AudioScheduledSourceNode {
         let this = Trusted::new(self);
         let global = self.global();
         let window = global.as_window();
-        let task_source = window.dom_manipulation_task_source();
-        let canceller = window.task_canceller(TaskSourceName::DOMManipulation);
+        let (task_source, canceller) = window
+            .task_manager()
+            .dom_manipulation_task_source_with_canceller();
         let callback = OnEndedCallback::new(move || {
             let _ = task_source.queue_with_canceller(
                 task!(ended: move || {
                     let this = this.root();
                     let global = this.global();
                     let window = global.as_window();
-                    window.dom_manipulation_task_source().queue_simple_event(
+                    window.task_manager().dom_manipulation_task_source().queue_simple_event(
                         this.upcast(),
                         atom!("ended"),
                         &window

components/script/dom/baseaudiocontext.rs

@@ -40,7 +40,7 @@ use crate::dom::oscillatornode::OscillatorNode;
 use crate::dom::pannernode::PannerNode;
 use crate::dom::promise::Promise;
 use crate::dom::window::Window;
-use crate::task_source::{TaskSource, TaskSourceName};
+use crate::task_source::TaskSource;
 use dom_struct::dom_struct;
 use js::rust::CustomAutoRooterGuard;
 use js::typedarray::ArrayBuffer;
@@ -213,7 +213,7 @@ impl BaseAudioContext {
     pub fn resume(&self) {
         let global = self.global();
         let window = global.as_window();
-        let task_source = window.dom_manipulation_task_source();
+        let task_source = window.task_manager().dom_manipulation_task_source();
         let this = Trusted::new(self);
         // Set the rendering thread state to 'running' and start
         // rendering the audio graph.
@@ -227,7 +227,7 @@ impl BaseAudioContext {
                             if this.state.get() != AudioContextState::Running {
                                 this.state.set(AudioContextState::Running);
                                 let window = DomRoot::downcast::<Window>(this.global()).unwrap();
-                                window.dom_manipulation_task_source().queue_simple_event(
+                                window.task_manager().dom_manipulation_task_source().queue_simple_event(
                                     this.upcast(),
                                     atom!("statechange"),
                                     &window
@@ -428,10 +428,12 @@ impl BaseAudioContextMethods for BaseAudioContext {
             let decoded_audio__ = decoded_audio.clone();
             let this = Trusted::new(self);
             let this_ = this.clone();
-            let task_source = window.dom_manipulation_task_source();
-            let task_source_ = window.dom_manipulation_task_source();
-            let canceller = window.task_canceller(TaskSourceName::DOMManipulation);
-            let canceller_ = window.task_canceller(TaskSourceName::DOMManipulation);
+            let (task_source, canceller) = window
+                .task_manager()
+                .dom_manipulation_task_source_with_canceller();
+            let (task_source_, canceller_) = window
+                .task_manager()
+                .dom_manipulation_task_source_with_canceller();
             let callbacks = AudioDecoderCallbacks::new()
                 .ready(move |channel_count| {
                     decoded_audio

components/script/dom/document.rs

@@ -521,6 +521,7 @@ impl Document {
                 if self.ready_state.get() == DocumentReadyState::Complete {
                     let document = Trusted::new(self);
                     self.window
+                        .task_manager()
                         .dom_manipulation_task_source()
                         .queue(
                             task!(fire_pageshow_event: move || {
@@ -1869,6 +1870,7 @@ impl Document {
         debug!("Document loads are complete.");
         let document = Trusted::new(self);
         self.window
+            .task_manager()
             .dom_manipulation_task_source()
             .queue(
                 task!(fire_load_event: move || {
@@ -1922,6 +1924,7 @@ impl Document {
         let document = Trusted::new(self);
         if document.root().browsing_context().is_some() {
             self.window
+                .task_manager()
                 .dom_manipulation_task_source()
                 .queue(
                     task!(fire_pageshow_event: move || {
@@ -2104,13 +2107,16 @@ impl Document {
 
         // Step 4.1.
         let window = self.window();
-        window.dom_manipulation_task_source().queue_event(
-            self.upcast(),
-            atom!("DOMContentLoaded"),
-            EventBubbles::Bubbles,
-            EventCancelable::NotCancelable,
-            window,
-        );
+        window
+            .task_manager()
+            .dom_manipulation_task_source()
+            .queue_event(
+                self.upcast(),
+                atom!("DOMContentLoaded"),
+                EventBubbles::Bubbles,
+                EventCancelable::NotCancelable,
+                window,
+            );
 
         window.reflow(ReflowGoal::Full, ReflowReason::DOMContentLoaded);
         update_with_current_time_ms(&self.dom_content_loaded_event_end);

components/script/dom/globalscope.rs

@@ -476,7 +476,7 @@ impl GlobalScope {
     /// this global scope.
     pub fn networking_task_source(&self) -> NetworkingTaskSource {
         if let Some(window) = self.downcast::<Window>() {
-            return window.networking_task_source();
+            return window.task_manager().networking_task_source();
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.networking_task_source();
@@ -488,7 +488,7 @@ impl GlobalScope {
     /// this global scope.
     pub fn remote_event_task_source(&self) -> RemoteEventTaskSource {
         if let Some(window) = self.downcast::<Window>() {
-            return window.remote_event_task_source();
+            return window.task_manager().remote_event_task_source();
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.remote_event_task_source();
@@ -500,7 +500,7 @@ impl GlobalScope {
     /// this global scope.
     pub fn websocket_task_source(&self) -> WebsocketTaskSource {
         if let Some(window) = self.downcast::<Window>() {
-            return window.websocket_task_source();
+            return window.task_manager().websocket_task_source();
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.websocket_task_source();
@@ -635,7 +635,7 @@ impl GlobalScope {
     /// properly cancelled when the global scope is destroyed.
     pub fn task_canceller(&self, name: TaskSourceName) -> TaskCanceller {
         if let Some(window) = self.downcast::<Window>() {
-            return window.task_canceller(name);
+            return window.task_manager().task_canceller(name);
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             // Note: the "name" is not passed to the worker,
@@ -691,7 +691,7 @@ impl GlobalScope {
 
     pub fn dom_manipulation_task_source(&self) -> DOMManipulationTaskSource {
         if let Some(window) = self.downcast::<Window>() {
-            return window.dom_manipulation_task_source();
+            return window.task_manager().dom_manipulation_task_source();
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.dom_manipulation_task_source();
@@ -703,7 +703,7 @@ impl GlobalScope {
     /// this of this global scope.
     pub fn file_reading_task_source(&self) -> FileReadingTaskSource {
         if let Some(window) = self.downcast::<Window>() {
-            return window.file_reading_task_source();
+            return window.task_manager().file_reading_task_source();
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.file_reading_task_source();
@@ -756,7 +756,7 @@ impl GlobalScope {
     /// of this global scope.
     pub fn performance_timeline_task_source(&self) -> PerformanceTimelineTaskSource {
         if let Some(window) = self.downcast::<Window>() {
-            return window.performance_timeline_task_source();
+            return window.task_manager().performance_timeline_task_source();
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.performance_timeline_task_source();

components/script/dom/htmldetailselement.rs

@@ -76,7 +76,7 @@ impl VirtualMethods for HTMLDetailsElement {
             let window = window_from_node(self);
             let this = Trusted::new(self);
             // FIXME(nox): Why are errors silenced here?
-            let _ = window.dom_manipulation_task_source().queue(
+            let _ = window.task_manager().dom_manipulation_task_source().queue(
                 task!(details_notification_task_steps: move || {
                     let this = this.root();
                     if counter == this.toggle_counter.get() {

components/script/dom/htmldialogelement.rs

@@ -90,7 +90,8 @@ impl HTMLDialogElementMethods for HTMLDialogElement {
         // TODO: Step 4 implement pending dialog stack removal
 
         // Step 5
-        win.dom_manipulation_task_source()
+        win.task_manager()
+            .dom_manipulation_task_source()
             .queue_simple_event(target, atom!("close"), &win);
     }
 }

components/script/dom/htmlformelement.rs

@@ -523,6 +523,7 @@ impl HTMLFormElement {
 
         // Step 3.
         target
+            .task_manager()
             .dom_manipulation_task_source()
             .queue(task, target.upcast())
             .unwrap();

components/script/dom/htmliframeelement.rs

@@ -237,7 +237,7 @@ impl HTMLIFrameElement {
             let this = Trusted::new(self);
             let pipeline_id = self.pipeline_id().unwrap();
             // FIXME(nox): Why are errors silenced here?
-            let _ = window.dom_manipulation_task_source().queue(
+            let _ = window.task_manager().dom_manipulation_task_source().queue(
                 task!(iframe_load_event_steps: move || {
                     this.root().iframe_load_event_steps(pipeline_id);
                 }),

components/script/dom/htmlimageelement.rs

@@ -40,7 +40,7 @@ use crate::dom::window::Window;
 use crate::microtask::{Microtask, MicrotaskRunnable};
 use crate::network_listener::{NetworkListener, PreInvoke};
 use crate::script_thread::ScriptThread;
-use crate::task_source::{TaskSource, TaskSourceName};
+use crate::task_source::TaskSource;
 use cssparser::{Parser, ParserInput};
 use dom_struct::dom_struct;
 use euclid::Point2D;
@@ -237,8 +237,9 @@ impl HTMLImageElement {
             let (responder_sender, responder_receiver) = ipc::channel().unwrap();
 
             let window = window_from_node(elem);
-            let task_source = window.networking_task_source();
-            let task_canceller = window.task_canceller(TaskSourceName::Networking);
+            let (task_source, canceller) = window
+                .task_manager()
+                .networking_task_source_with_canceller();
             let generation = elem.generation.get();
             ROUTER.add_route(
                 responder_receiver.to_opaque(),
@@ -257,7 +258,7 @@ impl HTMLImageElement {
                             element.process_image_response(image);
                         }
                     }),
-                        &task_canceller,
+                        &canceller,
                     );
                 }),
             );
@@ -308,10 +309,14 @@ impl HTMLImageElement {
         }));
 
         let (action_sender, action_receiver) = ipc::channel().unwrap();
+        let (task_source, canceller) = document
+            .window()
+            .task_manager()
+            .networking_task_source_with_canceller();
         let listener = NetworkListener {
-            context: context,
-            task_source: window.networking_task_source(),
-            canceller: Some(window.task_canceller(TaskSourceName::Networking)),
+            context,
+            task_source,
+            canceller: Some(canceller),
         };
         ROUTER.add_route(
             action_receiver.to_opaque(),
@@ -780,7 +785,7 @@ impl HTMLImageElement {
     fn update_the_image_data_sync_steps(&self) {
         let document = document_from_node(self);
         let window = document.window();
-        let task_source = window.dom_manipulation_task_source();
+        let task_source = window.task_manager().dom_manipulation_task_source();
         let this = Trusted::new(self);
         let (src, pixel_density) = match self.select_image_source() {
             // Step 8
@@ -938,7 +943,7 @@ impl HTMLImageElement {
                     current_request.current_pixel_density = pixel_density;
                     let this = Trusted::new(self);
                     let src = String::from(src);
-                    let _ = window.dom_manipulation_task_source().queue(
+                    let _ = window.task_manager().dom_manipulation_task_source().queue(
                         task!(image_load_event: move || {
                             let this = this.root();
                             {
@@ -989,8 +994,9 @@ impl HTMLImageElement {
             let (responder_sender, responder_receiver) = ipc::channel().unwrap();
 
             let window = window_from_node(elem);
-            let task_source = window.networking_task_source();
-            let task_canceller = window.task_canceller(TaskSourceName::Networking);
+            let (task_source, canceller) = window
+                .task_manager()
+                .networking_task_source_with_canceller();
             let generation = elem.generation.get();
             ROUTER.add_route(responder_receiver.to_opaque(), Box::new(move |message| {
                 debug!("Got image {:?}", message);
@@ -1008,7 +1014,7 @@ impl HTMLImageElement {
                             DOMString::from_string(selected_source_clone), generation, selected_pixel_density);
                         }
                     }),
-                    &task_canceller,
+                    &canceller,
                 );
             }));
 
@@ -1133,7 +1139,7 @@ impl HTMLImageElement {
         let this = Trusted::new(self);
         let window = window_from_node(self);
         let src = src.to_string();
-        let _ = window.dom_manipulation_task_source().queue(
+        let _ = window.task_manager().dom_manipulation_task_source().queue(
             task!(image_load_event: move || {
                 let this = this.root();
                 let relevant_mutation = this.generation.get() != generation;

components/script/dom/htmlinputelement.rs

@@ -1515,13 +1515,16 @@ impl VirtualMethods for HTMLInputElement {
         {
             if event.IsTrusted() {
                 let window = window_from_node(self);
-                let _ = window.user_interaction_task_source().queue_event(
-                    &self.upcast(),
-                    atom!("input"),
-                    EventBubbles::Bubbles,
-                    EventCancelable::NotCancelable,
-                    &window,
-                );
+                let _ = window
+                    .task_manager()
+                    .user_interaction_task_source()
+                    .queue_event(
+                        &self.upcast(),
+                        atom!("input"),
+                        EventBubbles::Bubbles,
+                        EventCancelable::NotCancelable,
+                        &window,
+                    );
             }
         }
     }