1 files changed, 8 insertions, 7 deletions

diff --git a/components/layout_2020/fragment_tree/box_fragment.rs b/components/layout_2020/fragment_tree/box_fragment.rs
index 22767a601f8..7d61e1e6807 100644
--- a/components/layout_2020/fragment_tree/box_fragment.rs
+++ b/components/layout_2020/fragment_tree/box_fragment.rs
@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use app_units::Au;
+use atomic_refcell::AtomicRefCell;
 use base::print_tree::PrintTree;
 use serde::Serialize;
 use servo_arc::Arc as ServoArc;
@@ -13,7 +14,6 @@ use style::properties::ComputedValues;
 use style::Zero;
 
 use super::{BaseFragment, BaseFragmentInfo, CollapsedBlockMargins, Fragment};
-use crate::cell::ArcRefCell;
 use crate::formatting_contexts::Baselines;
 use crate::fragment_tree::FragmentFlags;
 use crate::geom::{
@@ -53,7 +53,7 @@ pub(crate) struct BoxFragment {
 
     #[serde(skip_serializing)]
     pub style: ServoArc<ComputedValues>,
-    pub children: Vec<ArcRefCell<Fragment>>,
+    pub children: Vec<Fragment>,
 
     /// The content rect of this fragment in the parent fragment's content rectangle. This
     /// does not include padding, border, or margin -- it only includes content.
@@ -84,7 +84,8 @@ pub(crate) struct BoxFragment {
     /// The resolved box insets if this box is `position: sticky`. These are calculated
     /// during stacking context tree construction because they rely on the size of the
     /// scroll container.
-    pub(crate) resolved_sticky_insets: Option<PhysicalSides<AuOrAuto>>,
+    #[serde(skip_serializing)]
+    pub(crate) resolved_sticky_insets: AtomicRefCell<Option<PhysicalSides<AuOrAuto>>>,
 
     #[serde(skip_serializing)]
     pub background_mode: BackgroundMode,
@@ -115,7 +116,7 @@ impl BoxFragment {
         BoxFragment {
             base: base_fragment_info.into(),
             style,
-            children: children.into_iter().map(ArcRefCell::new).collect(),
+            children,
             content_rect,
             padding,
             border,
@@ -124,7 +125,7 @@ impl BoxFragment {
             baselines: Baselines::default(),
             block_margins_collapsed_with_children,
             scrollable_overflow_from_children,
-            resolved_sticky_insets: None,
+            resolved_sticky_insets: AtomicRefCell::default(),
             background_mode: BackgroundMode::Normal,
             detailed_layout_info: None,
         }
@@ -234,7 +235,7 @@ impl BoxFragment {
         ));
 
         for child in &self.children {
-            child.borrow().print(tree);
+            child.print(tree);
         }
         tree.end_level();
     }
@@ -278,7 +279,7 @@ impl BoxFragment {
             "Should not call this method on statically positioned box."
         );
 
-        if let Some(resolved_sticky_insets) = self.resolved_sticky_insets {
+        if let Some(resolved_sticky_insets) = *self.resolved_sticky_insets.borrow() {
             return resolved_sticky_insets;
         }