MessagePort: implement disentanglement (#36654)

Implement
[disentangle](https://html.spec.whatwg.org/multipage/#disentangle)
Remove bespoke gc logic which now becomes unnecessary. 
Adds a wpt test that hits the "disentangle while in transfer" logic.
Updates streams code, fixing an error where disentanglement is
conditional on an error.

Test coverage: there are existing tests in
`/webmessaging/message-channels/close-event/explicitly-closed.tentative.window.js`
for the no transfer case, and the simple completed transfer case, and
this PR adds a test for the more complicated transfer in progress case.

Fix https://github.com/servo/servo/issues/36465

---------

Signed-off-by: gterzian <2792687+gterzian@users.noreply.github.com>

components/script/dom/messageport.rs

@@ -83,6 +83,20 @@ impl MessagePort {
         *self.entangled_port.borrow_mut() = Some(other_id);
     }
 
+    /// <https://html.spec.whatwg.org/multipage/#disentangle>
+    pub(crate) fn disentangle(&self) -> Option<MessagePortId> {
+        // Disentangle initiatorPort and otherPort, so that they are no longer entangled or associated with each other.
+        // Note: called from `disentangle_port` in the global, where the rest happens.
+        self.entangled_port.borrow_mut().take()
+    }
+
+    /// Has the port been disentangled?
+    /// Used when starting the port to fire the `close` event,
+    /// to cover the case of a disentanglement while in transfer.
+    pub(crate) fn disentangled(&self) -> bool {
+        self.entangled_port.borrow().is_none()
+    }
+
     pub(crate) fn message_port_id(&self) -> &MessagePortId {
         &self.message_port_id
     }
@@ -314,20 +328,28 @@ impl MessagePortMethods<crate::DomTypeHolder> for MessagePort {
     }
 
     /// <https://html.spec.whatwg.org/multipage/#dom-messageport-start>
-    fn Start(&self) {
+    fn Start(&self, can_gc: CanGc) {
         if self.detached.get() {
             return;
         }
-        self.global().start_message_port(self.message_port_id());
+        self.global()
+            .start_message_port(self.message_port_id(), can_gc);
     }
 
     /// <https://html.spec.whatwg.org/multipage/#dom-messageport-close>
-    fn Close(&self) {
+    fn Close(&self, can_gc: CanGc) {
         if self.detached.get() {
             return;
         }
+
+        // Set this's [[Detached]] internal slot value to true.
         self.detached.set(true);
-        self.global().close_message_port(self.message_port_id());
+
+        let global = self.global();
+        global.close_message_port(self.message_port_id());
+
+        // If this is entangled, disentangle it.
+        global.disentangle_port(self, can_gc);
     }
 
     /// <https://html.spec.whatwg.org/multipage/#handler-messageport-onmessage>
@@ -340,15 +362,19 @@ impl MessagePortMethods<crate::DomTypeHolder> for MessagePort {
     }
 
     /// <https://html.spec.whatwg.org/multipage/#handler-messageport-onmessage>
-    fn SetOnmessage(&self, listener: Option<Rc<EventHandlerNonNull>>) {
+    fn SetOnmessage(&self, listener: Option<Rc<EventHandlerNonNull>>, can_gc: CanGc) {
         if self.detached.get() {
             return;
         }
         self.set_onmessage(listener);
         // Note: we cannot use the event_handler macro, due to the need to start the port.
-        self.global().start_message_port(self.message_port_id());
+        self.global()
+            .start_message_port(self.message_port_id(), can_gc);
     }
 
     // <https://html.spec.whatwg.org/multipage/#handler-messageport-onmessageerror>
     event_handler!(messageerror, GetOnmessageerror, SetOnmessageerror);
+
+    // <https://html.spec.whatwg.org/multipage/#handler-messageport-onclose>
+    event_handler!(close, GetOnclose, SetOnclose);
 }