Root nodes for the duration of their CSS transitions.

This ensures that we can pass a node address as part of the asynchronous
transition end notification, making it safe to fire the corresponding
DOM event on the node from the script thread. Without explicitly rooting
this node when the transition starts, we risk the node being GCed before
the transition is complete.

1 files changed, 4 insertions, 0 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 9e8cc9bc165..2bef4bc1c21 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -478,6 +478,7 @@ impl LayoutThread {
                     text_index_response: TextIndexResponse(None),
                     pending_images: vec![],
                     nodes_from_point_response: vec![],
+                    newly_transitioning_nodes: vec![],
                 })),
             error_reporter: CSSErrorReporter {
                 pipelineid: id,
@@ -1436,11 +1437,14 @@ impl LayoutThread {
                                                document: Option<&ServoLayoutDocument>,
                                                rw_data: &mut LayoutThreadData,
                                                context: &mut LayoutContext) {
+        assert!(rw_data.newly_transitioning_nodes.is_empty());
+
         // Kick off animations if any were triggered, expire completed ones.
         animation::update_animation_state(&self.constellation_chan,
                                           &self.script_chan,
                                           &mut *self.running_animations.write(),
                                           &mut *self.expired_animations.write(),
+                                          &mut rw_data.newly_transitioning_nodes,
                                           &self.new_animations_receiver,
                                           self.id,
                                           &self.timer);