Auto merge of #24664 - gterzian:fix_port_transfer, r=jdm

Fix loophole in messageport transfer

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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #24600 (GitHub issue number if applicable)

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- [ ] These changes do not require tests because ___

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components/script_traits/lib.rs

@@ -1042,8 +1042,12 @@ pub struct PortMessageTask {
 /// Messages for communication between the constellation and a global managing ports.
 #[derive(Debug, Deserialize, Serialize)]
 pub enum MessagePortMsg {
-    /// Enables a port to catch-up on messages that were sent while the transfer was ongoing.
-    CompleteTransfer(MessagePortId, VecDeque<PortMessageTask>),
+    /// Complete the transfer for a batch of ports.
+    CompleteTransfer(HashMap<MessagePortId, VecDeque<PortMessageTask>>),
+    /// 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),
     /// Handle a new port-message-task.