Add an ArcRefCell<T> type

components/layout_2020/cell.rs

@@ -0,0 +1,58 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use atomic_refcell::AtomicRefCell;
+use serde::{Serialize, Serializer};
+use servo_arc::Arc;
+use std::fmt;
+use std::ops::Deref;
+
+pub(crate) struct ArcRefCell<T> {
+    value: Arc<AtomicRefCell<T>>,
+}
+
+impl<T> ArcRefCell<T> {
+    pub fn new(value: T) -> Self {
+        Self {
+            value: Arc::new(AtomicRefCell::new(value)),
+        }
+    }
+}
+
+impl<T> Clone for ArcRefCell<T> {
+    fn clone(&self) -> Self {
+        Self {
+            value: self.value.clone(),
+        }
+    }
+}
+
+impl<T> Deref for ArcRefCell<T> {
+    type Target = AtomicRefCell<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.value
+    }
+}
+
+impl<T> fmt::Debug for ArcRefCell<T>
+where
+    T: fmt::Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        self.value.fmt(formatter)
+    }
+}
+
+impl<T> Serialize for ArcRefCell<T>
+where
+    T: Serialize,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.borrow().serialize(serializer)
+    }
+}

components/layout_2020/lib.rs

@@ -11,6 +11,7 @@ extern crate log;
 #[macro_use]
 extern crate serde;
 
+mod cell;
 pub mod context;
 pub mod data;
 pub mod display_list;