Auto merge of #11585 - asajeffrey:constellation-avoid-deadlock-during-pipeline-closure, r=larsbergstrom

Avoid deadlock when closing a pipeline.

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At the moment, the constellation blocks on a pipeline during closure. This PR makes pipeline closure asynchronous.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #11546.
- [X] These changes do not require tests because testing for absence of deadlock is difficult.

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1 files changed, 2 insertions, 0 deletions

diff --git a/components/script_traits/script_msg.rs b/components/script_traits/script_msg.rs
index d1f56a6e790..241833bc13f 100644
--- a/components/script_traits/script_msg.rs
+++ b/components/script_traits/script_msg.rs
@@ -110,6 +110,8 @@ pub enum ScriptMsg {
     TouchEventProcessed(EventResult),
     /// Get Scroll Offset
     GetScrollOffset(PipelineId, LayerId, IpcSender<Point2D<f32>>),
+    /// Notifies the constellation that this pipeline has exited.
+    PipelineExited(PipelineId),
     /// Requests that the compositor shut down.
     Exit,
 }