script: Refactor channels in ScriptThread into receivers and senders (#34776)

Create two new data structures in the `script` crate to hold senders and
receiver:

- `ScriptThreadSenders`: holds all outgoing channels from the
  `ScriptThread` including a channel to the `ScriptThread` itself. The
  ultimate goal with this is to reduce duplication by giving a boxed
  version of this this to `Window`s.
- `ScriptThradReceivers`: holds all incoming channels to the
  `ScriptThread`. This isn't cloenable like the senders. This is used to
  abstract away `recv()` and `try_recv()` methods used to make the
  `ScriptThread` event loop easier to read.

In addition:

- The many duplicated `ScriptThread` self-senders for the `TaskManager`
  have been removed and, in general, a lot of boilerplate is removed as
  well.
- Visibilty of all methods affected by this change is changed to
  `pub(crate)` in order to take advantage of dead code detection. Some
  dead code produced from macros is removed.
- Some conversion code is refactord into implementations of the `From`
  trait.
- The names of channels uses a standard "sender" and "receiver" naming
  as well as trying to be descriptive of where they go in `ScriptThread`
  as well as `InitialScriptState`

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

components/script/dom/abstractworkerglobalscope.rs

@@ -35,7 +35,7 @@ impl ScriptChan for SendableWorkerScriptChan {
         self.sender.send(msg).map_err(|_| ())
     }
 
-    fn clone(&self) -> Box<dyn ScriptChan + Send> {
+    fn as_boxed(&self) -> Box<dyn ScriptChan + Send> {
         Box::new(SendableWorkerScriptChan {
             sender: self.sender.clone(),
             worker: self.worker.clone(),
@@ -62,7 +62,7 @@ impl ScriptChan for WorkerThreadWorkerChan {
         self.sender.send(msg).map_err(|_| ())
     }
 
-    fn clone(&self) -> Box<dyn ScriptChan + Send> {
+    fn as_boxed(&self) -> Box<dyn ScriptChan + Send> {
         Box::new(WorkerThreadWorkerChan {
             sender: self.sender.clone(),
             worker: self.worker.clone(),

components/script/dom/dedicatedworkerglobalscope.rs

@@ -418,7 +418,7 @@ impl DedicatedWorkerGlobalScope {
                     worker_url,
                     devtools_mpsc_port,
                     runtime,
-                    parent_sender.clone(),
+                    parent_sender.as_boxed(),
                     own_sender,
                     receiver,
                     closing,

components/script/dom/document.rs

@@ -185,10 +185,11 @@ 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::network_listener::{NetworkListener, PreInvoke};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
 use crate::script_runtime::{CanGc, CommonScriptMsg, ScriptThreadEventCategory};
-use crate::script_thread::{with_script_thread, MainThreadScriptMsg, ScriptThread};
+use crate::script_thread::{with_script_thread, ScriptThread};
 use crate::stylesheet_set::StylesheetSetRef;
 use crate::task::TaskBox;
 use crate::task_source::{TaskSource, TaskSourceName};

components/script/dom/globalscope.rs

@@ -127,6 +127,7 @@ use crate::dom::webgpu::identityhub::IdentityHub;
 use crate::dom::window::Window;
 use crate::dom::workerglobalscope::WorkerGlobalScope;
 use crate::dom::workletglobalscope::WorkletGlobalScope;
+use crate::messaging::MainThreadScriptChan;
 use crate::microtask::{Microtask, MicrotaskQueue, UserMicrotask};
 use crate::network_listener::{NetworkListener, PreInvoke};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
@@ -134,7 +135,7 @@ use crate::script_module::{DynamicModuleList, ModuleScript, ModuleTree, ScriptFe
 use crate::script_runtime::{
     CanGc, CommonScriptMsg, JSContext as SafeJSContext, ScriptChan, ScriptPort, ThreadSafeJSContext,
 };
-use crate::script_thread::{with_script_thread, MainThreadScriptChan, ScriptThread};
+use crate::script_thread::{with_script_thread, ScriptThread};
 use crate::security_manager::CSPViolationReporter;
 use crate::task::TaskCanceller;
 use crate::task_source::dom_manipulation::DOMManipulationTaskSource;
@@ -2581,7 +2582,9 @@ impl GlobalScope {
     /// `ScriptChan` to send messages to the event loop of this global scope.
     pub fn script_chan(&self) -> Box<dyn ScriptChan + Send> {
         if let Some(window) = self.downcast::<Window>() {
-            return MainThreadScriptChan(window.main_thread_script_chan().clone()).clone();
+            return Box::new(
+                MainThreadScriptChan(window.main_thread_script_chan().clone()).clone(),
+            );
         }
         if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
             return worker.script_chan();

components/script/dom/paintworkletglobalscope.rs

@@ -86,7 +86,7 @@ pub struct PaintWorkletGlobalScope {
 
 impl PaintWorkletGlobalScope {
     #[allow(unsafe_code)]
-    pub fn new(
+    pub(crate) fn new(
         runtime: &Runtime,
         pipeline_id: PipelineId,
         base_url: ServoUrl,

components/script/dom/serviceworkerglobalscope.rs

@@ -143,7 +143,7 @@ impl ScriptChan for ServiceWorkerChan {
             .map_err(|_| ())
     }
 
-    fn clone(&self) -> Box<dyn ScriptChan + Send> {
+    fn as_boxed(&self) -> Box<dyn ScriptChan + Send> {
         Box::new(ServiceWorkerChan {
             sender: self.sender.clone(),
         })

components/script/dom/testworkletglobalscope.rs

@@ -31,7 +31,7 @@ pub struct TestWorkletGlobalScope {
 
 impl TestWorkletGlobalScope {
     #[allow(unsafe_code)]
-    pub fn new(
+    pub(crate) fn new(
         runtime: &Runtime,
         pipeline_id: PipelineId,
         base_url: ServoUrl,

components/script/dom/window.rs

@@ -145,15 +145,15 @@ use crate::dom::windowproxy::{WindowProxy, WindowProxyHandler};
 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,
+};
 use crate::microtask::MicrotaskQueue;
 use crate::realms::{enter_realm, InRealm};
 use crate::script_runtime::{
     CanGc, CommonScriptMsg, JSContext, Runtime, ScriptChan, ScriptPort, ScriptThreadEventCategory,
 };
-use crate::script_thread::{
-    ImageCacheMsg, MainThreadScriptChan, MainThreadScriptMsg, ScriptThread,
-    SendableMainThreadScriptChan,
-};
+use crate::script_thread::ScriptThread;
 use crate::task_manager::TaskManager;
 use crate::task_source::{TaskSource, TaskSourceName};
 use crate::timers::{IsInterval, TimerCallback};
@@ -453,7 +453,7 @@ impl Window {
         self.js_runtime.borrow()
     }
 
-    pub fn main_thread_script_chan(&self) -> &Sender<MainThreadScriptMsg> {
+    pub(crate) fn main_thread_script_chan(&self) -> &Sender<MainThreadScriptMsg> {
         &self.script_chan.0
     }
 
@@ -2683,7 +2683,7 @@ impl Window {
 impl Window {
     #[allow(unsafe_code)]
     #[allow(clippy::too_many_arguments)]
-    pub fn new(
+    pub(crate) fn new(
         runtime: Rc<Runtime>,
         script_chan: MainThreadScriptChan,
         task_manager: TaskManager,

components/script/dom/worklet.rs

@@ -49,9 +49,10 @@ use crate::dom::workletglobalscope::{
     WorkletGlobalScope, WorkletGlobalScopeInit, WorkletGlobalScopeType, WorkletTask,
 };
 use crate::fetch::load_whole_resource;
+use crate::messaging::MainThreadScriptMsg;
 use crate::realms::InRealm;
 use crate::script_runtime::{CanGc, CommonScriptMsg, Runtime, ScriptThreadEventCategory};
-use crate::script_thread::{MainThreadScriptMsg, ScriptThread};
+use crate::script_thread::ScriptThread;
 use crate::task::TaskBox;
 use crate::task_source::TaskSourceName;
 
@@ -277,7 +278,7 @@ impl Drop for WorkletThreadPool {
 impl WorkletThreadPool {
     /// Create a new thread pool and spawn the threads.
     /// When the thread pool is dropped, the threads will be asked to quit.
-    pub fn spawn(global_init: WorkletGlobalScopeInit) -> WorkletThreadPool {
+    pub(crate) fn spawn(global_init: WorkletGlobalScopeInit) -> WorkletThreadPool {
         let primary_role = WorkletThreadRole::new(false, false);
         let hot_backup_role = WorkletThreadRole::new(true, false);
         let cold_backup_role = WorkletThreadRole::new(false, true);

components/script/dom/workletglobalscope.rs

@@ -27,9 +27,9 @@ use crate::dom::testworkletglobalscope::{TestWorkletGlobalScope, TestWorkletTask
 #[cfg(feature = "webgpu")]
 use crate::dom::webgpu::identityhub::IdentityHub;
 use crate::dom::worklet::WorkletExecutor;
+use crate::messaging::MainThreadScriptMsg;
 use crate::script_module::ScriptFetchOptions;
 use crate::script_runtime::{CanGc, JSContext};
-use crate::script_thread::MainThreadScriptMsg;
 
 #[dom_struct]
 /// <https://drafts.css-houdini.org/worklets/#workletglobalscope>
@@ -49,7 +49,7 @@ pub struct WorkletGlobalScope {
 
 impl WorkletGlobalScope {
     /// Create a new heap-allocated `WorkletGlobalScope`.
-    pub fn new(
+    pub(crate) fn new(
         scope_type: WorkletGlobalScopeType,
         runtime: &Runtime,
         pipeline_id: PipelineId,
@@ -76,7 +76,7 @@ impl WorkletGlobalScope {
     }
 
     /// Create a new stack-allocated `WorkletGlobalScope`.
-    pub fn new_inherited(
+    pub(crate) fn new_inherited(
         pipeline_id: PipelineId,
         base_url: ServoUrl,
         executor: WorkletExecutor,
@@ -172,7 +172,7 @@ impl WorkletGlobalScope {
 
 /// Resources required by workletglobalscopes
 #[derive(Clone)]
-pub struct WorkletGlobalScopeInit {
+pub(crate) struct WorkletGlobalScopeInit {
     /// Channel to the main script thread
     pub to_script_thread_sender: Sender<MainThreadScriptMsg>,
     /// Channel to a resource thread