Fix warnings introduced in newer Rust Nightly

This does not (yet) upgrade ./rust-toolchain

The warnings:

* dead_code "field is never read"
* redundant_semicolons "unnecessary trailing semicolon"
* non_fmt_panic "panic message is not a string literal, this is no longer accepted in Rust 2021"
* unstable_name_collisions "a method with this name may be added to the standard library in the future"
* legacy_derive_helpers "derive helper attribute is used before it is introduced" https://github.com/rust-lang/rust/issues/79202

1 files changed, 0 insertions, 5 deletions

diff --git a/components/layout_thread_2020/lib.rs b/components/layout_thread_2020/lib.rs
index ce23c087056..41ceddc5d44 100644
--- a/components/layout_thread_2020/lib.rs
+++ b/components/layout_thread_2020/lib.rs
@@ -167,9 +167,6 @@ pub struct LayoutThread {
     /// The fragment tree.
     fragment_tree: RefCell<Option<Arc<FragmentTree>>>,
 
-    /// The document-specific shared lock used for author-origin stylesheets
-    document_shared_lock: Option<SharedRwLock>,
-
     /// A counter for epoch messages
     epoch: Cell<Epoch>,
 
@@ -510,7 +507,6 @@ impl LayoutThread {
             outstanding_web_fonts: Arc::new(AtomicUsize::new(0)),
             box_tree: Default::default(),
             fragment_tree: Default::default(),
-            document_shared_lock: None,
             // Epoch starts at 1 because of the initial display list for epoch 0 that we send to WR
             epoch: Cell::new(Epoch(1)),
             viewport_size: Size2D::new(Au(0), Au(0)),
@@ -947,7 +943,6 @@ impl LayoutThread {
         // Calculate the actual viewport as per DEVICE-ADAPT § 6
         // If the entire flow tree is invalid, then it will be reflowed anyhow.
         let document_shared_lock = document.style_shared_lock();
-        self.document_shared_lock = Some(document_shared_lock.clone());
         let author_guard = document_shared_lock.read();
 
         let ua_stylesheets = &*UA_STYLESHEETS;