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/shared/constellation/from_script_message.rs

@@ -4,7 +4,7 @@
 
 //! Messages send from the ScriptThread to the Constellation.
 
-use std::collections::{HashMap, VecDeque};
+use std::collections::HashMap;
 use std::fmt;
 
 use base::Epoch;
@@ -35,7 +35,9 @@ use webgpu_traits::{WebGPU, WebGPUAdapterResponse};
 use webrender_api::ImageKey;
 
 use crate::structured_data::{BroadcastMsg, StructuredSerializedData};
-use crate::{LogEntry, MessagePortMsg, PortMessageTask, TraversalDirection, WindowSizeType};
+use crate::{
+    LogEntry, MessagePortMsg, PortMessageTask, PortTransferInfo, TraversalDirection, WindowSizeType,
+};
 
 /// A Script to Constellation channel.
 #[derive(Clone, Debug, Deserialize, Serialize)]
@@ -470,7 +472,7 @@ pub enum ScriptToConstellationMessage {
         /* The ids of ports transferred successfully */
         Vec<MessagePortId>,
         /* The ids, and buffers, of ports whose transfer failed */
-        HashMap<MessagePortId, VecDeque<PortMessageTask>>,
+        HashMap<MessagePortId, PortTransferInfo>,
     ),
     /// A new message-port was created or transferred, with corresponding control-sender.
     NewMessagePort(MessagePortRouterId, MessagePortId),
@@ -482,10 +484,14 @@ pub enum ScriptToConstellationMessage {
     RerouteMessagePort(MessagePortId, PortMessageTask),
     /// A message-port was shipped, let the entangled port know.
     MessagePortShipped(MessagePortId),
-    /// A message-port has been discarded by script.
-    RemoveMessagePort(MessagePortId),
     /// Entangle two message-ports.
     EntanglePorts(MessagePortId, MessagePortId),
+    /// Disentangle two message-ports.
+    /// The first is the initiator, the second the other port,
+    /// unless the message is sent to complete a disentanglement,
+    /// in which case the first one is the other port,
+    /// and the second is none.
+    DisentanglePorts(MessagePortId, Option<MessagePortId>),
     /// A global has started managing broadcast-channels.
     NewBroadcastChannelRouter(
         BroadcastChannelRouterId,

components/shared/constellation/lib.rs

@@ -157,18 +157,29 @@ pub struct PortMessageTask {
     pub data: StructuredSerializedData,
 }
 
+/// The information needed by a global to process the transfer of a port.
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
+pub struct PortTransferInfo {
+    /// <https://html.spec.whatwg.org/multipage/#port-message-queue>
+    pub port_message_queue: VecDeque<PortMessageTask>,
+    /// A boolean indicating whether the port has been disentangled while in transfer,
+    /// if so, the disentanglement should be completed along with the transfer.
+    /// <https://html.spec.whatwg.org/multipage/#disentangle>
+    pub disentangled: bool,
+}
+
 /// Messages for communication between the constellation and a global managing ports.
 #[derive(Debug, Deserialize, Serialize)]
 #[allow(clippy::large_enum_variant)]
 pub enum MessagePortMsg {
     /// Complete the transfer for a batch of ports.
-    CompleteTransfer(HashMap<MessagePortId, VecDeque<PortMessageTask>>),
+    CompleteTransfer(HashMap<MessagePortId, PortTransferInfo>),
     /// Complete the transfer of a single port,
     /// whose transfer was pending because it had been requested
     /// while a previous failed transfer was being rolled-back.
-    CompletePendingTransfer(MessagePortId, VecDeque<PortMessageTask>),
-    /// Remove a port, the entangled one doesn't exists anymore.
-    RemoveMessagePort(MessagePortId),
+    CompletePendingTransfer(MessagePortId, PortTransferInfo),
+    /// <https://html.spec.whatwg.org/multipage/#disentangle>
+    CompleteDisentanglement(MessagePortId),
     /// Handle a new port-message-task.
     NewTask(MessagePortId, PortMessageTask),
 }

components/shared/constellation/structured_data/transferable.rs

@@ -77,7 +77,12 @@ impl MessagePortImpl {
         self.entangled_port
     }
 
-    /// Entanged this port with another.
+    /// <https://html.spec.whatwg.org/multipage/#disentangle>
+    pub fn disentangle(&mut self) -> Option<MessagePortId> {
+        self.entangled_port.take()
+    }
+
+    /// <https://html.spec.whatwg.org/multipage/#entangle>
     pub fn entangle(&mut self, other_id: MessagePortId) {
         self.entangled_port = Some(other_id);
     }