Use std::cell::OnceCell and remove mitochondria dependency (#30207)

`OnceCell` is now part of the standard library and we'll be able to use
it once we upgrade rust. For now we can use the version that's shipped
behind a feature flag in rust. This removes a dependency on one crate.

Cargo.lock

@@ -3129,7 +3129,6 @@ dependencies = [
  "lazy_static",
  "libc",
  "log",
- "mitochondria",
  "msg",
  "net_traits",
  "parking_lot",
@@ -3735,12 +3734,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "mitochondria"
-version = "1.1.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9de3eca27871df31c33b807f834b94ef7d000956f57aa25c5aed9c5f0aae8f6f"
-
 [[package]]
 name = "mozangle"
 version = "0.3.5"
@@ -4991,7 +4984,6 @@ dependencies = [
  "metrics",
  "mime",
  "mime_guess",
- "mitochondria",
  "mozangle",
  "mozjs",
  "msg",

Cargo.toml

@@ -49,7 +49,6 @@ log = "0.4"
 malloc_size_of_derive = "0.1"
 mime = "0.3.13"
 mime_guess = "2.0.3"
-mitochondria = "1.1.2"
 mozangle = "0.3"
 num-traits = "0.2"
 parking_lot = "0.12"

components/layout_2020/Cargo.toml

@@ -28,7 +28,6 @@ html5ever = { workspace = true }
 ipc-channel = { workspace = true }
 libc = { workspace = true }
 log = { workspace = true }
-mitochondria = { workspace = true }
 msg = { path = "../msg" }
 net_traits = { path = "../net_traits" }
 parking_lot = { workspace = true }

components/layout_2020/display_list/mod.rs

@@ -13,10 +13,10 @@ use embedder_traits::Cursor;
 use euclid::{Point2D, SideOffsets2D, Size2D};
 use fnv::FnvHashMap;
 use gfx::text::glyph::GlyphStore;
-use mitochondria::OnceCell;
 use msg::constellation_msg::BrowsingContextId;
 use net_traits::image_cache::UsePlaceholder;
 use script_traits::compositor::{CompositorDisplayListInfo, ScrollTreeNodeId};
+use std::cell::OnceCell;
 use std::sync::Arc;
 use style::computed_values::text_decoration_style::T as ComputedTextDecorationStyle;
 use style::dom::OpaqueNode;
@@ -440,7 +440,7 @@ impl<'a> BuilderForBoxFragment<'a> {
     }
 
     fn content_rect(&self) -> &units::LayoutRect {
-        self.content_rect.init_once(|| {
+        self.content_rect.get_or_init(|| {
             self.fragment
                 .content_rect
                 .to_physical(self.fragment.style.writing_mode, self.containing_block)
@@ -450,7 +450,7 @@ impl<'a> BuilderForBoxFragment<'a> {
     }
 
     fn padding_rect(&self) -> &units::LayoutRect {
-        self.padding_rect.init_once(|| {
+        self.padding_rect.get_or_init(|| {
             self.fragment
                 .padding_rect()
                 .to_physical(self.fragment.style.writing_mode, self.containing_block)
@@ -462,11 +462,11 @@ impl<'a> BuilderForBoxFragment<'a> {
     fn border_edge_clip(&self, builder: &mut DisplayListBuilder) -> Option<wr::ClipId> {
         *self
             .border_edge_clip_id
-            .init_once(|| clip_for_radii(self.border_radius, self.border_rect, builder))
+            .get_or_init(|| clip_for_radii(self.border_radius, self.border_rect, builder))
     }
 
     fn padding_edge_clip(&self, builder: &mut DisplayListBuilder) -> Option<wr::ClipId> {
-        *self.padding_edge_clip_id.init_once(|| {
+        *self.padding_edge_clip_id.get_or_init(|| {
             clip_for_radii(
                 inner_radii(
                     self.border_radius,
@@ -482,7 +482,7 @@ impl<'a> BuilderForBoxFragment<'a> {
     }
 
     fn content_edge_clip(&self, builder: &mut DisplayListBuilder) -> Option<wr::ClipId> {
-        *self.content_edge_clip_id.init_once(|| {
+        *self.content_edge_clip_id.get_or_init(|| {
             clip_for_radii(
                 inner_radii(
                     self.border_radius,

components/layout_2020/lib.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 #![deny(unsafe_code)]
+#![feature(once_cell)]
 
 #[macro_use]
 extern crate log;

components/script/Cargo.toml

@@ -76,7 +76,6 @@ media = { path = "../media" }
 metrics = { path = "../metrics" }
 mime = { workspace = true }
 mime_guess = { workspace = true }
-mitochondria = { workspace = true }
 msg = { path = "../msg" }
 net_traits = { path = "../net_traits" }
 num-traits = { workspace = true }

components/script/dom/bindings/root.rs

@@ -33,9 +33,8 @@ use crate::dom::node::Node;
 use js::jsapi::{Heap, JSObject, JSTracer};
 use js::rust::GCMethods;
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
-use mitochondria::OnceCell;
 use script_layout_interface::TrustedNodeAddress;
-use std::cell::{Cell, UnsafeCell};
+use std::cell::{Cell, OnceCell, UnsafeCell};
 use std::default::Default;
 use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
@@ -718,7 +717,7 @@ where
         F: FnOnce() -> DomRoot<T>,
     {
         assert_in_script();
-        &self.ptr.init_once(|| Dom::from_ref(&cb()))
+        &self.ptr.get_or_init(|| Dom::from_ref(&cb()))
     }
 }
 
@@ -742,7 +741,7 @@ impl<T: DomObject> MallocSizeOf for DomOnceCell<T> {
 #[allow(unrooted_must_root)]
 unsafe impl<T: DomObject> JSTraceable for DomOnceCell<T> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
-        if let Some(ptr) = self.ptr.as_ref() {
+        if let Some(ptr) = self.ptr.get() {
             ptr.trace(trc);
         }
     }

components/script/lib.rs

@@ -4,6 +4,7 @@
 
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]
+#![feature(once_cell)]
 #![feature(plugin)]
 #![feature(register_tool)]
 #![deny(unsafe_code)]