layout: Remove the obsolete layout tracing functionality (#35001)

There were two kinds of layout tracing controlled by the same debugging
option:

 - modern layout: Functionality that dumped a JSON serialization of the
   layout tree before and after layout.
 - legacy layout: A scope based tracing that reported the process of
   layout in a structured way.

I don't think anyone working on layout is using either of these two
features. For modern layout requiring data structure to implement
`serde` serialization is incredibly inconvenient and also generates a
lot of extra code.

We also have a more modern tracing functionality based on perfetto that
we have started to use for layout and IMO it's actually being used and
more robust.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

45 files changed, 64 insertions, 675 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 5dfd24d8b97..0e46b2816d6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4005,8 +4005,6 @@ dependencies = [
  "rayon",
  "script_layout_interface",
  "selectors",
- "serde",
- "serde_json",
  "servo_arc",
  "servo_config",
  "servo_geometry",
diff --git a/components/layout/block.rs b/components/layout/block.rs
index 43817cbbc25..df1f9b8085d 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -67,8 +67,8 @@ use crate::incremental::RelayoutMode;
 use crate::model::{
     AdjoiningMargins, CollapsibleMargins, IntrinsicISizes, MarginCollapseInfo, MaybeAuto,
 };
+use crate::sequential;
 use crate::traversal::PreorderFlowTraversal;
-use crate::{layout_debug, layout_debug_scope, sequential};
 
 /// Information specific to floated blocks.
 #[derive(Clone, Serialize)]
@@ -922,8 +922,6 @@ impl BlockFlow {
         mut fragmentation_context: Option<FragmentationContext>,
         margins_may_collapse: MarginsMayCollapseFlag,
     ) -> Option<Arc<dyn Flow>> {
-        let _scope = layout_debug_scope!("assign_block_size_block_base {:x}", self.base.debug_id());
-
         let mut break_at = None;
         let content_box = self.fragment.content_box();
         if self
@@ -1861,8 +1859,6 @@ impl BlockFlow {
 
     /// Computes intrinsic inline sizes for a block.
     pub fn bubble_inline_sizes_for_block(&mut self, consult_children: bool) {
-        let _scope = layout_debug_scope!("block::bubble_inline_sizes {:x}", self.base.debug_id());
-
         let mut flags = self.base.flags;
         if self.definitely_has_zero_block_size() {
             // This is kind of a hack for Acid2. But it's a harmless one, because (a) this behavior
@@ -2186,8 +2182,6 @@ impl Flow for BlockFlow {
     /// Dual fragments consume some inline-size first, and the remainder is assigned to all child
     /// (block) contexts.
     fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!("block::assign_inline_sizes {:x}", self.base.debug_id());
-
         let shared_context = layout_context.shared_context();
         self.compute_inline_sizes(shared_context);
 
@@ -2277,11 +2271,6 @@ impl Flow for BlockFlow {
         fragmentation_context: Option<FragmentationContext>,
     ) -> Option<Arc<dyn Flow>> {
         if self.fragment.is_replaced() {
-            let _scope = layout_debug_scope!(
-                "assign_replaced_block_size_if_necessary {:x}",
-                self.base.debug_id()
-            );
-
             // Assign block-size for fragment if it is an image fragment.
             self.fragment.assign_replaced_block_size_if_necessary();
             if !self
@@ -2315,10 +2304,6 @@ impl Flow for BlockFlow {
         {
             // Root element margins should never be collapsed according to CSS § 8.3.1.
             debug!("{}", self.is_root());
-            debug!(
-                "assign_block_size: assigning block_size for root flow {:#x?}",
-                self.base().debug_id()
-            );
             trace!("BlockFlow before assigning: {:?}", &self);
             let flow = self.assign_block_size_block_base(
                 layout_context,
@@ -2328,10 +2313,6 @@ impl Flow for BlockFlow {
             trace!("BlockFlow after assigning: {:?}", &self);
             flow
         } else {
-            debug!(
-                "assign_block_size: assigning block_size for block {:#x?}",
-                self.base().debug_id()
-            );
             trace!("BlockFlow before assigning: {:?}", &self);
             let flow = self.assign_block_size_block_base(
                 layout_context,
@@ -2660,13 +2641,7 @@ impl Flow for BlockFlow {
 
 impl fmt::Debug for BlockFlow {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "{:?}({:x}) {:?}",
-            self.class(),
-            self.base.debug_id(),
-            self.base
-        )
+        write!(f, "{:?} {:?}", self.class(), self.base)
     }
 }
 
diff --git a/components/layout/construct.rs b/components/layout/construct.rs
index 74e2400faa0..c73c534e50d 100644
--- a/components/layout/construct.rs
+++ b/components/layout/construct.rs
@@ -97,14 +97,6 @@ impl ConstructionResult {
         // inefficient!
         (*self).clone()
     }
-
-    pub fn debug_id(&self) -> usize {
-        match *self {
-            ConstructionResult::None => 0,
-            ConstructionResult::ConstructionItem(_) => 0,
-            ConstructionResult::Flow(ref flow_ref, _) => flow_ref.base().debug_id(),
-        }
-    }
 }
 
 /// Represents the output of flow construction for a DOM node that has not yet resulted in a
diff --git a/components/layout/flex.rs b/components/layout/flex.rs
index 87408ad66f1..7e422078967 100644
--- a/components/layout/flex.rs
+++ b/components/layout/flex.rs
@@ -32,7 +32,6 @@ use crate::model::{
     self, AdjoiningMargins, CollapsibleMargins, IntrinsicISizes, MaybeAuto, SizeConstraint,
 };
 use crate::traversal::PreorderFlowTraversal;
-use crate::{layout_debug, layout_debug_scope};
 
 /// The size of an axis. May be a specified size, a min/max
 /// constraint, or an unlimited size
@@ -513,7 +512,6 @@ impl FlexFlow {
         inline_end_content_edge: Au,
         content_inline_size: Au,
     ) {
-        let _scope = layout_debug_scope!("flex::block_mode_assign_inline_sizes");
         debug!("flex::block_mode_assign_inline_sizes");
 
         // FIXME (mbrubeck): Get correct mode for absolute containing block
@@ -560,7 +558,6 @@ impl FlexFlow {
         _inline_end_content_edge: Au,
         content_inline_size: Au,
     ) {
-        let _scope = layout_debug_scope!("flex::inline_mode_assign_inline_sizes");
         debug!("inline_mode_assign_inline_sizes");
 
         debug!("content_inline_size = {:?}", content_inline_size);
@@ -718,8 +715,6 @@ impl FlexFlow {
     }
 
     fn inline_mode_assign_block_size(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!("flex::inline_mode_assign_block_size");
-
         let line_count = self.lines.len() as i32;
         let line_align = {
             let line_align = self
@@ -932,11 +927,6 @@ impl Flow for FlexFlow {
     }
 
     fn bubble_inline_sizes(&mut self) {
-        let _scope = layout_debug_scope!(
-            "flex::bubble_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
-
         // Flexbox Section 9.0: Generate anonymous flex items:
         // This part was handled in the flow constructor.
 
@@ -968,10 +958,6 @@ impl Flow for FlexFlow {
     }
 
     fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!(
-            "flex::assign_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
         debug!("assign_inline_sizes");
 
         if !self
diff --git a/components/layout/flow.rs b/components/layout/flow.rs
index b5140f8e8e7..ac167aad890 100644
--- a/components/layout/flow.rs
+++ b/components/layout/flow.rs
@@ -1010,7 +1010,6 @@ impl fmt::Debug for BaseFlow {
 impl Serialize for BaseFlow {
     fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
         let mut serializer = serializer.serialize_struct("base", 5)?;
-        serializer.serialize_field("id", &self.debug_id())?;
         serializer.serialize_field(
             "stacking_relative_position",
             &self.stacking_relative_position,
@@ -1187,11 +1186,6 @@ impl BaseFlow {
         self.children.iter_mut()
     }
 
-    pub fn debug_id(&self) -> usize {
-        let p = self as *const _;
-        p as usize
-    }
-
     pub fn collect_stacking_contexts_for_children(
         &mut self,
         state: &mut StackingContextCollectionState,
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index e750f08d61d..b50add41e98 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -66,8 +66,6 @@ use crate::inline::{
     InlineFragmentContext, InlineFragmentNodeFlags, InlineFragmentNodeInfo, InlineMetrics,
     LineMetrics,
 };
-#[cfg(debug_assertions)]
-use crate::layout_debug;
 use crate::model::{
     self, style_length, IntrinsicISizes, IntrinsicISizesContribution, MaybeAuto, SizeConstraint,
 };
@@ -151,11 +149,6 @@ pub struct Fragment {
     /// Various flags for this fragment.
     pub flags: FragmentFlags,
 
-    /// A debug ID that is consistent for the life of this fragment (via transform etc).
-    /// This ID should not be considered stable across multiple layouts or fragment
-    /// manipulations.
-    debug_id: DebugId,
-
     /// The ID of the StackingContext that contains this fragment. This is initialized
     /// to 0, but it assigned during the collect_stacking_contexts phase of display
     /// list construction.
@@ -170,7 +163,6 @@ pub struct Fragment {
 impl Serialize for Fragment {
     fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
         let mut serializer = serializer.serialize_struct("fragment", 3)?;
-        serializer.serialize_field("id", &self.debug_id)?;
         serializer.serialize_field("border_box", &self.border_box)?;
         serializer.serialize_field("margin", &self.margin)?;
         serializer.end()
@@ -699,7 +691,6 @@ impl Fragment {
             inline_context: None,
             pseudo: node.get_pseudo_element_type(),
             flags,
-            debug_id: DebugId::new(),
             stacking_context_id: StackingContextId::root(),
             established_reference_frame: None,
         }
@@ -730,7 +721,6 @@ impl Fragment {
             inline_context: None,
             pseudo,
             flags: FragmentFlags::empty(),
-            debug_id: DebugId::new(),
             stacking_context_id: StackingContextId::root(),
             established_reference_frame: None,
         }
@@ -757,7 +747,6 @@ impl Fragment {
             inline_context: None,
             pseudo: self.pseudo,
             flags: FragmentFlags::empty(),
-            debug_id: DebugId::new(),
             stacking_context_id: StackingContextId::root(),
             established_reference_frame: None,
         }
@@ -784,7 +773,6 @@ impl Fragment {
             inline_context: self.inline_context.clone(),
             pseudo: self.pseudo,
             flags: FragmentFlags::empty(),
-            debug_id: self.debug_id.clone(),
             stacking_context_id: StackingContextId::root(),
             established_reference_frame: None,
         }
@@ -3274,14 +3262,13 @@ impl fmt::Debug for Fragment {
 
         write!(
             f,
-            "\n{}({}) [{:?}]\
+            "\n{} [{:?}]\
             \nborder_box={:?}\
             {border_padding_string}\
             {margin_string}\
             {damage_string}\
             {flags_string}",
             self.specific.get_type(),
-            self.debug_id,
             self.specific,
             self.border_box,
         )
@@ -3447,53 +3434,3 @@ pub struct SpeculatedInlineContentEdgeOffsets {
     pub start: Au,
     pub end: Au,
 }
-
-#[cfg(not(debug_assertions))]
-#[derive(Clone)]
-struct DebugId;
-
-#[cfg(debug_assertions)]
-#[derive(Clone)]
-struct DebugId(u16);
-
-#[cfg(not(debug_assertions))]
-impl DebugId {
-    pub fn new() -> DebugId {
-        DebugId
-    }
-}
-
-#[cfg(debug_assertions)]
-impl DebugId {
-    pub fn new() -> DebugId {
-        DebugId(layout_debug::generate_unique_debug_id())
-    }
-}
-
-#[cfg(not(debug_assertions))]
-impl fmt::Display for DebugId {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{:p}", &self)
-    }
-}
-
-#[cfg(debug_assertions)]
-impl fmt::Display for DebugId {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.0)
-    }
-}
-
-#[cfg(not(debug_assertions))]
-impl Serialize for DebugId {
-    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
-        serializer.serialize_str(&format!("{:p}", &self))
-    }
-}
-
-#[cfg(debug_assertions)]
-impl Serialize for DebugId {
-    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
-        serializer.serialize_u16(self.0)
-    }
-}
diff --git a/components/layout/inline.rs b/components/layout/inline.rs
index aa851a29ed3..e72a0d1524a 100644
--- a/components/layout/inline.rs
+++ b/components/layout/inline.rs
@@ -50,7 +50,7 @@ use crate::fragment::{
 };
 use crate::model::IntrinsicISizesContribution;
 use crate::traversal::PreorderFlowTraversal;
-use crate::{layout_debug, layout_debug_scope, text, ServoArc};
+use crate::{text, ServoArc};
 
 /// `Line`s are represented as offsets into the child list, rather than
 /// as an object that "owns" fragments. Choosing a different set of line
@@ -1479,8 +1479,6 @@ impl Flow for InlineFlow {
     fn bubble_inline_sizes(&mut self) {
         self.update_restyle_damage();
 
-        let _scope = layout_debug_scope!("inline::bubble_inline_sizes {:x}", self.base.debug_id());
-
         let writing_mode = self.base.writing_mode;
         for kid in self.base.child_iter_mut() {
             kid.mut_base().floats = Floats::new(writing_mode);
@@ -1579,8 +1577,6 @@ impl Flow for InlineFlow {
     /// Recursively (top-down) determines the actual inline-size of child contexts and fragments.
     /// When called on this context, the context has had its inline-size set by the parent context.
     fn assign_inline_sizes(&mut self, _: &LayoutContext) {
-        let _scope = layout_debug_scope!("inline::assign_inline_sizes {:x}", self.base.debug_id());
-
         // Initialize content fragment inline-sizes if they haven't been initialized already.
         //
         // TODO: Combine this with `LineBreaker`'s walk in the fragment list, or put this into
@@ -1623,8 +1619,6 @@ impl Flow for InlineFlow {
     /// Note that we do not need to do in-order traversal because the children
     /// are always block formatting context.
     fn assign_block_size(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!("inline::assign_block_size {:x}", self.base.debug_id());
-
         // Divide the fragments into lines.
         //
         // TODO(pcwalton, #226): Get the CSS `line-height` property from the
@@ -2044,13 +2038,7 @@ impl Flow for InlineFlow {
 
 impl fmt::Debug for InlineFlow {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "{:?}({:x}) {:?}",
-            self.class(),
-            self.base.debug_id(),
-            self.base()
-        )
+        write!(f, "{:?} {:?}", self.class(), self.base())
     }
 }
 
diff --git a/components/layout/layout_debug.rs b/components/layout/layout_debug.rs
deleted file mode 100644
index a50b92948a5..00000000000
--- a/components/layout/layout_debug.rs
+++ /dev/null
@@ -1,127 +0,0 @@
-/* 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/. */
-
-//! Supports writing a trace file created during each layout scope
-//! that can be viewed by an external tool to make layout debugging easier.
-
-use std::borrow::ToOwned;
-use std::cell::RefCell;
-use std::fs::File;
-use std::io::Write;
-#[cfg(debug_assertions)]
-use std::sync::atomic::{AtomicUsize, Ordering};
-
-use serde::Serialize;
-use serde_json::{to_string, to_value, Value};
-
-use crate::flow::GetBaseFlow;
-use crate::flow_ref::FlowRef;
-
-thread_local!(static STATE_KEY: RefCell<Option<State>> = const { RefCell::new(None) });
-
-#[cfg(debug_assertions)]
-static DEBUG_ID_COUNTER: AtomicUsize = AtomicUsize::new(0);
-
-pub struct Scope;
-
-#[macro_export]
-macro_rules! layout_debug_scope(
-    ($($arg:tt)*) => (
-        if cfg!(debug_assertions) {
-            layout_debug::Scope::new(format!($($arg)*))
-        } else {
-            layout_debug::Scope
-        }
-    )
-);
-
-#[derive(Serialize)]
-struct ScopeData {
-    name: String,
-    pre: Value,
-    post: Value,
-    children: Vec<ScopeData>,
-}
-
-impl ScopeData {
-    fn new(name: String, pre: Value) -> ScopeData {
-        ScopeData {
-            name,
-            pre,
-            post: Value::Null,
-            children: vec![],
-        }
-    }
-}
-
-struct State {
-    flow_root: FlowRef,
-    scope_stack: Vec<ScopeData>,
-}
-
-/// A layout debugging scope. The entire state of the flow tree
-/// will be output at the beginning and end of this scope.
-impl Scope {
-    pub fn new(name: String) -> Scope {
-        STATE_KEY.with(|r| {
-            if let Some(ref mut state) = *r.borrow_mut() {
-                let flow_trace = to_value(state.flow_root.base()).unwrap();
-                let data = Box::new(ScopeData::new(name.clone(), flow_trace));
-                state.scope_stack.push(*data);
-            }
-        });
-        Scope
-    }
-}
-
-#[cfg(debug_assertions)]
-impl Drop for Scope {
-    fn drop(&mut self) {
-        STATE_KEY.with(|r| {
-            if let Some(ref mut state) = *r.borrow_mut() {
-                let mut current_scope = state.scope_stack.pop().unwrap();
-                current_scope.post = to_value(state.flow_root.base()).unwrap();
-                let previous_scope = state.scope_stack.last_mut().unwrap();
-                previous_scope.children.push(current_scope);
-            }
-        });
-    }
-}
-
-/// Generate a unique ID. This is used for items such as Fragment
-/// which are often reallocated but represent essentially the
-/// same data.
-#[cfg(debug_assertions)]
-pub fn generate_unique_debug_id() -> u16 {
-    DEBUG_ID_COUNTER.fetch_add(1, Ordering::SeqCst) as u16
-}
-
-/// Begin a layout debug trace. If this has not been called,
-/// creating debug scopes has no effect.
-pub fn begin_trace(flow_root: FlowRef) {
-    assert!(STATE_KEY.with(|r| r.borrow().is_none()));
-
-    STATE_KEY.with(|r| {
-        let flow_trace = to_value(flow_root.base()).unwrap();
-        let state = State {
-            scope_stack: vec![*Box::new(ScopeData::new("root".to_owned(), flow_trace))],
-            flow_root: flow_root.clone(),
-        };
-        *r.borrow_mut() = Some(state);
-    });
-}
-
-/// End the debug layout trace. This will write the layout
-/// trace to disk in the current directory. The output
-/// file can then be viewed with an external tool.
-pub fn end_trace(generation: u32) {
-    let mut thread_state = STATE_KEY.with(|r| r.borrow_mut().take().unwrap());
-    assert_eq!(thread_state.scope_stack.len(), 1);
-    let mut root_scope = thread_state.scope_stack.pop().unwrap();
-    root_scope.post = to_value(thread_state.flow_root.base()).unwrap();
-
-    let result = to_string(&root_scope).unwrap();
-    let mut file = File::create(format!("layout_trace-{}.json", generation)).unwrap();
-    file.write_all(result.as_bytes()).unwrap();
-}
diff --git a/components/layout/lib.rs b/components/layout/lib.rs
index af624c58628..9990578c4f5 100644
--- a/components/layout/lib.rs
+++ b/components/layout/lib.rs
@@ -4,8 +4,6 @@
 
 #![deny(unsafe_code)]
 
-pub mod layout_debug;
-
 mod block;
 pub mod construct;
 pub mod context;
diff --git a/components/layout/table.rs b/components/layout/table.rs
index 859d3c47516..a2f4bab8cca 100644
--- a/components/layout/table.rs
+++ b/components/layout/table.rs
@@ -41,7 +41,6 @@ use crate::table_row::{
     TableRowSizeData,
 };
 use crate::table_wrapper::TableLayout;
-use crate::{layout_debug, layout_debug_scope};
 
 #[allow(unsafe_code)]
 unsafe impl crate::flow::HasBaseFlow for TableFlow {}
@@ -292,11 +291,6 @@ impl Flow for TableFlow {
     /// The maximum min/pref inline-sizes of each column are set from the rows for the automatic
     /// table layout calculation.
     fn bubble_inline_sizes(&mut self) {
-        let _scope = layout_debug_scope!(
-            "table::bubble_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
-
         // Get column inline sizes from colgroups
         for kid in self
             .block_flow
@@ -415,10 +409,6 @@ impl Flow for TableFlow {
     /// Recursively (top-down) determines the actual inline-size of child contexts and fragments.
     /// When called on this context, the context has had its inline-size set by the parent context.
     fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!(
-            "table::assign_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
         debug!(
             "assign_inline_sizes({}): assigning inline_size for flow",
             "table"
diff --git a/components/layout/table_cell.rs b/components/layout/table_cell.rs
index 0faeb8c1c6e..eda92b61b61 100644
--- a/components/layout/table_cell.rs
+++ b/components/layout/table_cell.rs
@@ -27,7 +27,6 @@ use crate::flow::{Flow, FlowClass, FlowFlags, GetBaseFlow, OpaqueFlow};
 use crate::fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
 use crate::table::InternalTable;
 use crate::table_row::{CollapsedBorder, CollapsedBorderFrom};
-use crate::{layout_debug, layout_debug_scope};
 
 #[allow(unsafe_code)]
 unsafe impl crate::flow::HasBaseFlow for TableCellFlow {}
@@ -199,11 +198,6 @@ impl Flow for TableCellFlow {
     /// Minimum/preferred inline-sizes set by this function are used in automatic table layout
     /// calculation.
     fn bubble_inline_sizes(&mut self) {
-        let _scope = layout_debug_scope!(
-            "table_cell::bubble_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
-
         self.block_flow.bubble_inline_sizes_for_block(true);
         let specified_inline_size = self
             .block_flow
@@ -250,10 +244,6 @@ impl Flow for TableCellFlow {
     /// When called on this context, the context has had its inline-size set by the parent table
     /// row.
     fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!(
-            "table_cell::assign_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
         debug!(
             "assign_inline_sizes({}): assigning inline_size for flow",
             "table_cell"
diff --git a/components/layout/table_colgroup.rs b/components/layout/table_colgroup.rs
index bf9f189602f..a378a42ec88 100644
--- a/components/layout/table_colgroup.rs
+++ b/components/layout/table_colgroup.rs
@@ -16,7 +16,6 @@ use crate::context::LayoutContext;
 use crate::display_list::{DisplayListBuildState, StackingContextCollectionState};
 use crate::flow::{BaseFlow, Flow, FlowClass, ForceNonfloatedFlag, OpaqueFlow};
 use crate::fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
-use crate::{layout_debug, layout_debug_scope};
 
 #[allow(unsafe_code)]
 unsafe impl crate::flow::HasBaseFlow for TableColGroupFlow {}
@@ -69,11 +68,6 @@ impl Flow for TableColGroupFlow {
     }
 
     fn bubble_inline_sizes(&mut self) {
-        let _scope = layout_debug_scope!(
-            "table_colgroup::bubble_inline_sizes {:x}",
-            self.base.debug_id()
-        );
-
         for fragment in &self.cols {
             // Retrieve the specified value from the appropriate CSS property.
             let inline_size = fragment.style().content_inline_size();
diff --git a/components/layout/table_row.rs b/components/layout/table_row.rs
index 246e3a7bdd1..c6b894a1fc6 100644
--- a/components/layout/table_row.rs
+++ b/components/layout/table_row.rs
@@ -32,7 +32,6 @@ use crate::flow_list::MutFlowListIterator;
 use crate::fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
 use crate::table::{ColumnComputedInlineSize, ColumnIntrinsicInlineSize, InternalTable, VecExt};
 use crate::table_cell::{CollapsedBordersForCell, TableCellFlow};
-use crate::{layout_debug, layout_debug_scope};
 
 #[allow(unsafe_code)]
 unsafe impl crate::flow::HasBaseFlow for TableRowFlow {}
@@ -372,11 +371,6 @@ impl Flow for TableRowFlow {
     /// The specified column inline-sizes of children cells are used in fixed table layout
     /// calculation.
     fn bubble_inline_sizes(&mut self) {
-        let _scope = layout_debug_scope!(
-            "table_row::bubble_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
-
         // Bubble up the specified inline-sizes from child table cells.
         let (mut min_inline_size, mut pref_inline_size) = (Au(0), Au(0));
         let collapsing_borders = self
@@ -466,10 +460,6 @@ impl Flow for TableRowFlow {
     }
 
     fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!(
-            "table_row::assign_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
         debug!(
             "assign_inline_sizes({}): assigning inline_size for flow",
             "table_row"
diff --git a/components/layout/table_rowgroup.rs b/components/layout/table_rowgroup.rs
index 4a21856b9f8..d21301b1004 100644
--- a/components/layout/table_rowgroup.rs
+++ b/components/layout/table_rowgroup.rs
@@ -24,7 +24,6 @@ use crate::display_list::{
 use crate::flow::{Flow, FlowClass, OpaqueFlow};
 use crate::fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
 use crate::table::{ColumnIntrinsicInlineSize, InternalTable, TableLikeFlow};
-use crate::{layout_debug, layout_debug_scope};
 
 #[allow(unsafe_code)]
 unsafe impl crate::flow::HasBaseFlow for TableRowGroupFlow {}
@@ -122,10 +121,6 @@ impl Flow for TableRowGroupFlow {
     }
 
     fn bubble_inline_sizes(&mut self) {
-        let _scope = layout_debug_scope!(
-            "table_rowgroup::bubble_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
         // Proper calculation of intrinsic sizes in table layout requires access to the entire
         // table, which we don't have yet. Defer to our parent.
     }
@@ -133,10 +128,6 @@ impl Flow for TableRowGroupFlow {
     /// Recursively (top-down) determines the actual inline-size of child contexts and fragments.
     /// When called on this context, the context has had its inline-size set by the parent context.
     fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!(
-            "table_rowgroup::assign_inline_sizes {:x}",
-            self.block_flow.base.debug_id()
-        );
         debug!(
             "assign_inline_sizes({}): assigning inline_size for flow",
             "table_rowgroup"
diff --git a/components/layout/traversal.rs b/components/layout/traversal.rs
index 0d33c02e068..f045cc9d856 100644
--- a/components/layout/traversal.rs
+++ b/components/layout/traversal.rs
@@ -224,11 +224,7 @@ fn construct_flows_at<'dom>(context: &LayoutContext, node: impl LayoutNode<'dom>
             let mut flow_constructor = FlowConstructor::new(context);
             if nonincremental_layout || !flow_constructor.repair_if_possible(&tnode) {
                 flow_constructor.process(&tnode);
-                debug!(
-                    "Constructed flow for {:?}: {:x}",
-                    tnode,
-                    tnode.flow_debug_id()
-                );
+                debug!("Constructed flow for {:?}", tnode,);
             }
         }
 
diff --git a/components/layout/wrapper.rs b/components/layout/wrapper.rs
index 2a10e9103a5..adb78b777cf 100644
--- a/components/layout/wrapper.rs
+++ b/components/layout/wrapper.rs
@@ -44,7 +44,6 @@ use crate::data::{InnerLayoutData, LayoutData, LayoutDataFlags};
 pub trait ThreadSafeLayoutNodeHelpers<'dom> {
     fn borrow_layout_data(self) -> Option<AtomicRef<'dom, InnerLayoutData>>;
     fn mutate_layout_data(self) -> Option<AtomicRefMut<'dom, InnerLayoutData>>;
-    fn flow_debug_id(self) -> usize;
 
     /// Returns the layout data flags for this node.
     fn flags(self) -> LayoutDataFlags;
@@ -83,11 +82,6 @@ where
             .map(|data| data.0.borrow_mut())
     }
 
-    fn flow_debug_id(self) -> usize {
-        self.borrow_layout_data()
-            .map_or(0, |d| d.flow_construction_result.debug_id())
-    }
-
     fn flags(self) -> LayoutDataFlags {
         self.borrow_layout_data().as_ref().unwrap().flags
     }
diff --git a/components/layout_2020/Cargo.toml b/components/layout_2020/Cargo.toml
index 2abc3a751d2..eda1e185bab 100644
--- a/components/layout_2020/Cargo.toml
+++ b/components/layout_2020/Cargo.toml
@@ -41,8 +41,6 @@ range = { path = "../range" }
 rayon = { workspace = true }
 script_layout_interface = { workspace = true }
 selectors = { workspace = true }
-serde = { workspace = true }
-serde_json = { workspace = true }
 servo_arc = { workspace = true }
 servo_config = { path = "../config" }
 servo_geometry = { path = "../geometry" }
@@ -51,7 +49,7 @@ style = { workspace = true }
 style_traits = { workspace = true }
 taffy = { workspace = true }
 tracing = { workspace = true, optional = true }
-unicode-bidi = { workspace = true, features = ["with_serde"] }
+unicode-bidi = { workspace = true }
 unicode-script = { workspace = true }
 url = { workspace = true }
 webrender_api = { workspace = true }
diff --git a/components/layout_2020/cell.rs b/components/layout_2020/cell.rs
index 5c1dd09ff44..910a6ab2104 100644
--- a/components/layout_2020/cell.rs
+++ b/components/layout_2020/cell.rs
@@ -6,7 +6,6 @@ use std::fmt;
 use std::ops::Deref;
 
 use atomic_refcell::AtomicRefCell;
-use serde::{Serialize, Serializer};
 use servo_arc::Arc;
 
 pub(crate) struct ArcRefCell<T> {
@@ -56,15 +55,3 @@ where
         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)
-    }
-}
diff --git a/components/layout_2020/flexbox/geom.rs b/components/layout_2020/flexbox/geom.rs
index 9e18561d8bd..6a302e27486 100644
--- a/components/layout_2020/flexbox/geom.rs
+++ b/components/layout_2020/flexbox/geom.rs
@@ -4,7 +4,6 @@
 
 //! <https://drafts.csswg.org/css-flexbox/#box-model>
 
-use serde::Serialize;
 use style::properties::longhands::flex_direction::computed_value::T as FlexDirection;
 
 use crate::geom::{LogicalRect, LogicalSides, LogicalVec2};
@@ -68,7 +67,7 @@ impl<T> FlexRelativeSides<T> {
 
 /// One of the two bits set by the `flex-direction` property
 /// (The other is "forward" v.s. reverse.)
-#[derive(Clone, Copy, Debug, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub(super) enum FlexAxis {
     /// The main axis is the inline axis of the container (not necessarily of flex items!),
     /// cross is block.
@@ -79,7 +78,7 @@ pub(super) enum FlexAxis {
 
 /// Which flow-relative sides map to the main-start and cross-start sides, respectively.
 /// See <https://drafts.csswg.org/css-flexbox/#box-model>
-#[derive(Clone, Copy, Debug, Serialize)]
+#[derive(Clone, Copy, Debug)]
 pub(super) enum MainStartCrossStart {
     InlineStartBlockStart,
     InlineStartBlockEnd,
diff --git a/components/layout_2020/flexbox/mod.rs b/components/layout_2020/flexbox/mod.rs
index 06cffac3df9..32c1023214f 100644
--- a/components/layout_2020/flexbox/mod.rs
+++ b/components/layout_2020/flexbox/mod.rs
@@ -4,7 +4,6 @@
 
 use app_units::Au;
 use geom::{FlexAxis, MainStartCrossStart};
-use serde::Serialize;
 use servo_arc::Arc as ServoArc;
 use style::logical_geometry::WritingMode;
 use style::properties::longhands::align_items::computed_value::T as AlignItems;
@@ -30,7 +29,7 @@ mod layout;
 
 /// A structure to hold the configuration of a flex container for use during layout
 /// and preferred width calculation.
-#[derive(Clone, Debug, Serialize)]
+#[derive(Clone, Debug)]
 pub(crate) struct FlexContainerConfig {
     container_is_single_line: bool,
     writing_mode: WritingMode,
@@ -88,11 +87,10 @@ impl FlexContainerConfig {
     }
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct FlexContainer {
     children: Vec<ArcRefCell<FlexLevelBox>>,
 
-    #[serde(skip_serializing)]
     style: ServoArc<ComputedValues>,
 
     /// The configuration of this [`FlexContainer`].
@@ -143,16 +141,14 @@ impl FlexContainer {
     }
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum FlexLevelBox {
     FlexItem(FlexItemBox),
     OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
 }
 
-#[derive(Serialize)]
 pub(crate) struct FlexItemBox {
     independent_formatting_context: IndependentFormattingContext,
-    #[serde(skip)]
     block_content_size_cache: ArcRefCell<Option<CachedBlockSizeContribution>>,
 }
 
diff --git a/components/layout_2020/flow/float.rs b/components/layout_2020/flow/float.rs
index c5eff328767..0967ad3006a 100644
--- a/components/layout_2020/flow/float.rs
+++ b/components/layout_2020/flow/float.rs
@@ -13,7 +13,6 @@ use std::ops::Range;
 
 use app_units::{Au, MAX_AU, MIN_AU};
 use euclid::num::Zero;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::computed_values::float::T as FloatProperty;
 use style::computed_values::position::T as Position;
@@ -33,7 +32,7 @@ use crate::style_ext::{DisplayInside, PaddingBorderMargin};
 use crate::ContainingBlock;
 
 /// A floating box.
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct FloatBox {
     /// The formatting context that makes up the content of this box.
     pub contents: IndependentFormattingContext,
diff --git a/components/layout_2020/flow/inline/inline_box.rs b/components/layout_2020/flow/inline/inline_box.rs
index 57a86cd31e2..2bb5a92d2b0 100644
--- a/components/layout_2020/flow/inline/inline_box.rs
+++ b/components/layout_2020/flow/inline/inline_box.rs
@@ -6,7 +6,6 @@ use std::vec::IntoIter;
 
 use app_units::Au;
 use fonts::FontMetrics;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::properties::ComputedValues;
 
@@ -19,10 +18,9 @@ use crate::fragment_tree::BaseFragmentInfo;
 use crate::style_ext::{ComputedValuesExt, PaddingBorderMargin};
 use crate::ContainingBlock;
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct InlineBox {
     pub base_fragment_info: BaseFragmentInfo,
-    #[serde(skip_serializing)]
     pub style: Arc<ComputedValues>,
     /// The identifier of this inline box in the containing [`super::InlineFormattingContext`].
     pub(super) identifier: InlineBoxIdentifier,
@@ -56,7 +54,7 @@ impl InlineBox {
     }
 }
 
-#[derive(Debug, Default, Serialize)]
+#[derive(Debug, Default)]
 pub(crate) struct InlineBoxes {
     /// A collection of all inline boxes in a particular [`super::InlineFormattingContext`].
     inline_boxes: Vec<ArcRefCell<InlineBox>>,
@@ -158,7 +156,7 @@ impl InlineBoxes {
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub(super) enum InlineBoxTreePathToken {
     Start(InlineBoxIdentifier),
     End(InlineBoxIdentifier),
@@ -179,7 +177,7 @@ impl InlineBoxTreePathToken {
 /// [`u32`] is used for the index, in order to save space. The value refers to the token
 /// in the start tree data structure which can be fetched to find the actual index of
 /// of the [`InlineBox`] in [`InlineBoxes::inline_boxes`].
-#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq)]
 pub(crate) struct InlineBoxIdentifier {
     pub index_of_start_in_tree: u32,
     pub index_in_inline_boxes: u32,
diff --git a/components/layout_2020/flow/inline/mod.rs b/components/layout_2020/flow/inline/mod.rs
index 1af7841c234..4b138bfbd14 100644
--- a/components/layout_2020/flow/inline/mod.rs
+++ b/components/layout_2020/flow/inline/mod.rs
@@ -88,7 +88,6 @@ use line::{
     TextRunLineItem,
 };
 use line_breaker::LineBreaker;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::computed_values::text_wrap_mode::T as TextWrapMode;
 use style::computed_values::vertical_align::T as VerticalAlign;
@@ -134,7 +133,7 @@ use crate::{ConstraintSpace, ContainingBlock};
 static FONT_SUBSCRIPT_OFFSET_RATIO: f32 = 0.20;
 static FONT_SUPERSCRIPT_OFFSET_RATIO: f32 = 0.34;
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct InlineFormattingContext {
     /// All [`InlineItem`]s in this [`InlineFormattingContext`] stored in a flat array.
     /// [`InlineItem::StartInlineBox`] and [`InlineItem::EndInlineBox`] allow representing
@@ -171,14 +170,14 @@ pub(crate) struct InlineFormattingContext {
 }
 
 /// A collection of data used to cache [`FontMetrics`] in the [`InlineFormattingContext`]
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct FontKeyAndMetrics {
     pub key: FontInstanceKey,
     pub pt_size: Au,
     pub metrics: FontMetrics,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum InlineItem {
     StartInlineBox(ArcRefCell<InlineBox>),
     EndInlineBox,
diff --git a/components/layout_2020/flow/inline/text_run.rs b/components/layout_2020/flow/inline/text_run.rs
index 412e9d4e54a..78160337396 100644
--- a/components/layout_2020/flow/inline/text_run.rs
+++ b/components/layout_2020/flow/inline/text_run.rs
@@ -13,7 +13,6 @@ use fonts::{
 use fonts_traits::ByteIndex;
 use log::warn;
 use range::Range as ServoRange;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::computed_values::text_rendering::T as TextRendering;
 use style::computed_values::white_space_collapse::T as WhiteSpaceCollapse;
@@ -38,10 +37,9 @@ pub(crate) const XI_LINE_BREAKING_CLASS_WJ: u8 = 30;
 pub(crate) const XI_LINE_BREAKING_CLASS_ZWJ: u8 = 42;
 
 /// <https://www.w3.org/TR/css-display-3/#css-text-run>
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct TextRun {
     pub base_fragment_info: BaseFragmentInfo,
-    #[serde(skip_serializing)]
     pub parent_style: Arc<ComputedValues>,
     pub text_range: Range<usize>,
 
@@ -64,14 +62,13 @@ enum SegmentStartSoftWrapPolicy {
     FollowLinebreaker,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct TextRunSegment {
     /// The index of this font in the parent [`super::InlineFormattingContext`]'s collection of font
     /// information.
     pub font_index: usize,
 
     /// The [`Script`] of this segment.
-    #[serde(skip_serializing)]
     pub script: Script,
 
     /// The bidi Level of this segment.
diff --git a/components/layout_2020/flow/mod.rs b/components/layout_2020/flow/mod.rs
index 686ac85838a..06f9da7d326 100644
--- a/components/layout_2020/flow/mod.rs
+++ b/components/layout_2020/flow/mod.rs
@@ -8,7 +8,6 @@
 use app_units::{Au, MAX_AU};
 use inline::InlineFormattingContext;
 use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
-use serde::Serialize;
 use servo_arc::Arc;
 use style::computed_values::clear::T as StyleClear;
 use style::properties::ComputedValues;
@@ -53,13 +52,13 @@ mod root;
 pub(crate) use construct::BlockContainerBuilder;
 pub use root::{BoxTree, CanvasBackground};
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct BlockFormattingContext {
     pub contents: BlockContainer,
     pub contains_floats: bool,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum BlockContainer {
     BlockLevelBoxes(Vec<ArcRefCell<BlockLevelBox>>),
     InlineFormattingContext(InlineFormattingContext),
@@ -76,7 +75,7 @@ impl BlockContainer {
     }
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum BlockLevelBox {
     Independent(IndependentFormattingContext),
     OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
@@ -231,9 +230,8 @@ pub(crate) struct CollapsibleWithParentStartMargin(bool);
 
 /// The contentes of a BlockContainer created to render a list marker
 /// for a list that has `list-style-position: outside`.
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct OutsideMarker {
-    #[serde(skip_serializing)]
     pub marker_style: Arc<ComputedValues>,
     pub base: LayoutBoxBase,
     pub block_container: BlockContainer,
diff --git a/components/layout_2020/flow/root.rs b/components/layout_2020/flow/root.rs
index 078b225bac5..b80b106da1e 100644
--- a/components/layout_2020/flow/root.rs
+++ b/components/layout_2020/flow/root.rs
@@ -8,7 +8,6 @@ use script_layout_interface::wrapper_traits::{
     LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode,
 };
 use script_layout_interface::{LayoutElementType, LayoutNodeType};
-use serde::Serialize;
 use servo_arc::Arc;
 use style::dom::OpaqueNode;
 use style::properties::ComputedValues;
@@ -33,7 +32,6 @@ use crate::style_ext::{ComputedValuesExt, Display, DisplayGeneratingBox, Display
 use crate::taffy::{TaffyItemBox, TaffyItemBoxInner};
 use crate::DefiniteContainingBlock;
 
-#[derive(Serialize)]
 pub struct BoxTree {
     /// Contains typically exactly one block-level box, which was generated by the root element.
     /// There may be zero if that element has `display: none`.
@@ -409,7 +407,7 @@ impl BoxTree {
 }
 
 /// <https://drafts.csswg.org/css-backgrounds/#root-background>
-#[derive(Clone, Serialize)]
+#[derive(Clone)]
 pub struct CanvasBackground {
     /// DOM node for the root element
     pub root_element: OpaqueNode,
@@ -420,7 +418,6 @@ pub struct CanvasBackground {
     pub from_element: OpaqueNode,
 
     /// The computed styles to take background properties from.
-    #[serde(skip)]
     pub style: Option<Arc<ComputedValues>>,
 }
 
diff --git a/components/layout_2020/formatting_contexts.rs b/components/layout_2020/formatting_contexts.rs
index e1d5b68a83d..8c0a5987956 100644
--- a/components/layout_2020/formatting_contexts.rs
+++ b/components/layout_2020/formatting_contexts.rs
@@ -3,7 +3,6 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use app_units::Au;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::properties::ComputedValues;
 use style::selector_parser::PseudoElement;
@@ -28,13 +27,13 @@ use crate::taffy::TaffyContainer;
 use crate::{ConstraintSpace, ContainingBlock, IndefiniteContainingBlock, LogicalVec2};
 
 /// <https://drafts.csswg.org/css-display/#independent-formatting-context>
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct IndependentFormattingContext {
     pub base: LayoutBoxBase,
     pub contents: IndependentFormattingContextContents,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum IndependentFormattingContextContents {
     NonReplaced(IndependentNonReplacedContents),
     Replaced(ReplacedContents),
@@ -42,7 +41,7 @@ pub(crate) enum IndependentFormattingContextContents {
 
 // Private so that code outside of this module cannot match variants.
 // It should got through methods instead.
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum IndependentNonReplacedContents {
     Flow(BlockFormattingContext),
     Flex(FlexContainer),
@@ -53,7 +52,7 @@ pub(crate) enum IndependentNonReplacedContents {
 
 /// The baselines of a layout or a [`crate::fragment_tree::BoxFragment`]. Some layout
 /// uses the first and some layout uses the last.
-#[derive(Clone, Copy, Debug, Default, Serialize)]
+#[derive(Clone, Copy, Debug, Default)]
 pub(crate) struct Baselines {
     pub first: Option<Au>,
     pub last: Option<Au>,
diff --git a/components/layout_2020/fragment_tree/base_fragment.rs b/components/layout_2020/fragment_tree/base_fragment.rs
index 4c1efaf0677..6404c340c00 100644
--- a/components/layout_2020/fragment_tree/base_fragment.rs
+++ b/components/layout_2020/fragment_tree/base_fragment.rs
@@ -4,25 +4,19 @@
 
 use bitflags::bitflags;
 use script_layout_interface::{combine_id_with_fragment_type, FragmentType};
-use serde::Serialize;
 use style::dom::OpaqueNode;
 use style::selector_parser::PseudoElement;
 
-use crate::layout_debug::DebugId;
-
 /// This data structure stores fields that are common to all non-base
 /// Fragment types and should generally be the first member of all
 /// concrete fragments.
-#[derive(Clone, Debug, Serialize)]
+#[derive(Clone, Debug)]
 pub(crate) struct BaseFragment {
     /// A tag which identifies the DOM node and pseudo element of this
     /// Fragment's content. If this fragment isn't related to any DOM
     /// node at all, the tag will be None.
     pub tag: Option<Tag>,
 
-    /// An id used to uniquely identify this Fragment in debug builds.
-    pub debug_id: DebugId,
-
     /// Flags which various information about this fragment used during
     /// layout.
     pub flags: FragmentFlags,
@@ -32,7 +26,6 @@ impl BaseFragment {
     pub(crate) fn anonymous() -> Self {
         BaseFragment {
             tag: None,
-            debug_id: DebugId::new(),
             flags: FragmentFlags::empty(),
         }
     }
@@ -45,7 +38,7 @@ impl BaseFragment {
 }
 
 /// Information necessary to construct a new BaseFragment.
-#[derive(Clone, Copy, Debug, Serialize)]
+#[derive(Clone, Copy, Debug)]
 pub(crate) struct BaseFragmentInfo {
     /// The tag to use for the new BaseFragment, if it is not an anonymous Fragment.
     pub tag: Option<Tag>,
@@ -74,7 +67,6 @@ impl From<BaseFragmentInfo> for BaseFragment {
     fn from(info: BaseFragmentInfo) -> Self {
         Self {
             tag: info.tag,
-            debug_id: DebugId::new(),
             flags: info.flags,
         }
     }
@@ -82,7 +74,7 @@ impl From<BaseFragmentInfo> for BaseFragment {
 
 bitflags! {
     /// Flags used to track various information about a DOM node during layout.
-    #[derive(Clone, Copy, Debug, Serialize)]
+    #[derive(Clone, Copy, Debug)]
     pub(crate) struct FragmentFlags: u8 {
         /// Whether or not the node that created this fragment is a `<body>` element on an HTML document.
         const IS_BODY_ELEMENT_OF_HTML_ELEMENT_ROOT = 1 << 0;
@@ -113,7 +105,7 @@ bitflags! {
 
 /// A data structure used to hold DOM and pseudo-element information about
 /// a particular layout object.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub(crate) struct Tag {
     pub(crate) node: OpaqueNode,
     pub(crate) pseudo: Option<PseudoElement>,
diff --git a/components/layout_2020/fragment_tree/box_fragment.rs b/components/layout_2020/fragment_tree/box_fragment.rs
index 7d61e1e6807..a0d86f290ee 100644
--- a/components/layout_2020/fragment_tree/box_fragment.rs
+++ b/components/layout_2020/fragment_tree/box_fragment.rs
@@ -5,7 +5,6 @@
 use app_units::Au;
 use atomic_refcell::AtomicRefCell;
 use base::print_tree::PrintTree;
-use serde::Serialize;
 use servo_arc::Arc as ServoArc;
 use style::computed_values::overflow_x::T as ComputedOverflow;
 use style::computed_values::position::T as ComputedPosition;
@@ -47,11 +46,9 @@ pub(crate) enum SpecificLayoutInfo {
     TableOrTableCell(Box<SpecificTableOrTableCellInfo>),
 }
 
-#[derive(Serialize)]
 pub(crate) struct BoxFragment {
     pub base: BaseFragment,
 
-    #[serde(skip_serializing)]
     pub style: ServoArc<ComputedValues>,
     pub children: Vec<Fragment>,
 
@@ -84,14 +81,11 @@ 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.
-    #[serde(skip_serializing)]
     pub(crate) resolved_sticky_insets: AtomicRefCell<Option<PhysicalSides<AuOrAuto>>>,
 
-    #[serde(skip_serializing)]
     pub background_mode: BackgroundMode,
 
     /// Additional information of from layout that could be used by Javascripts and devtools.
-    #[serde(skip_serializing)]
     pub detailed_layout_info: Option<SpecificLayoutInfo>,
 }
 
diff --git a/components/layout_2020/fragment_tree/fragment.rs b/components/layout_2020/fragment_tree/fragment.rs
index 5c8b86d455b..fdc8f75bb9a 100644
--- a/components/layout_2020/fragment_tree/fragment.rs
+++ b/components/layout_2020/fragment_tree/fragment.rs
@@ -5,10 +5,9 @@
 use std::sync::Arc;
 
 use app_units::Au;
-use base::id::{BrowsingContextId, PipelineId};
+use base::id::PipelineId;
 use base::print_tree::PrintTree;
 use fonts::{FontMetrics, GlyphStore};
-use serde::Serialize;
 use servo_arc::Arc as ServoArc;
 use style::properties::ComputedValues;
 use style::values::specified::text::TextDecorationLine;
@@ -23,7 +22,7 @@ use crate::cell::ArcRefCell;
 use crate::geom::{LogicalSides, PhysicalRect};
 use crate::style_ext::ComputedValuesExt;
 
-#[derive(Clone, Serialize)]
+#[derive(Clone)]
 pub(crate) enum Fragment {
     Box(ArcRefCell<BoxFragment>),
     /// Floating content. A floated fragment is very similar to a normal
@@ -46,27 +45,23 @@ pub(crate) enum Fragment {
     IFrame(ArcRefCell<IFrameFragment>),
 }
 
-#[derive(Serialize)]
 pub(crate) struct CollapsedBlockMargins {
     pub collapsed_through: bool,
     pub start: CollapsedMargin,
     pub end: CollapsedMargin,
 }
 
-#[derive(Clone, Copy, Debug, Serialize)]
+#[derive(Clone, Copy, Debug)]
 pub(crate) struct CollapsedMargin {
     max_positive: Au,
     min_negative: Au,
 }
 
-#[derive(Serialize)]
 pub(crate) struct TextFragment {
     pub base: BaseFragment,
-    #[serde(skip_serializing)]
     pub parent_style: ServoArc<ComputedValues>,
     pub rect: PhysicalRect<Au>,
     pub font_metrics: FontMetrics,
-    #[serde(skip_serializing)]
     pub font_key: FontInstanceKey,
     pub glyphs: Vec<Arc<GlyphStore>>,
 
@@ -77,24 +72,18 @@ pub(crate) struct TextFragment {
     pub justification_adjustment: Au,
 }
 
-#[derive(Serialize)]
 pub(crate) struct ImageFragment {
     pub base: BaseFragment,
-    #[serde(skip_serializing)]
     pub style: ServoArc<ComputedValues>,
     pub rect: PhysicalRect<Au>,
     pub clip: PhysicalRect<Au>,
-    #[serde(skip_serializing)]
     pub image_key: Option<ImageKey>,
 }
 
-#[derive(Serialize)]
 pub(crate) struct IFrameFragment {
     pub base: BaseFragment,
     pub pipeline_id: PipelineId,
-    pub browsing_context_id: BrowsingContextId,
     pub rect: PhysicalRect<Au>,
-    #[serde(skip_serializing)]
     pub style: ServoArc<ComputedValues>,
 }
 
diff --git a/components/layout_2020/fragment_tree/fragment_tree.rs b/components/layout_2020/fragment_tree/fragment_tree.rs
index 35718c708b9..545eef2df0f 100644
--- a/components/layout_2020/fragment_tree/fragment_tree.rs
+++ b/components/layout_2020/fragment_tree/fragment_tree.rs
@@ -6,7 +6,6 @@ use app_units::Au;
 use base::print_tree::PrintTree;
 use euclid::default::{Point2D, Rect, Size2D};
 use fxhash::FxHashSet;
-use serde::Serialize;
 use style::animation::AnimationSetKey;
 use style::dom::OpaqueNode;
 use webrender_api::units;
@@ -17,7 +16,6 @@ use crate::display_list::StackingContext;
 use crate::flow::CanvasBackground;
 use crate::geom::PhysicalRect;
 
-#[derive(Serialize)]
 pub struct FragmentTree {
     /// Fragments at the top-level of the tree.
     ///
@@ -37,7 +35,6 @@ pub struct FragmentTree {
     pub(crate) initial_containing_block: PhysicalRect<Au>,
 
     /// <https://drafts.csswg.org/css-backgrounds/#special-backgrounds>
-    #[serde(skip)]
     pub(crate) canvas_background: CanvasBackground,
 
     /// Whether or not the root element is sensitive to scroll input events.
diff --git a/components/layout_2020/fragment_tree/hoisted_shared_fragment.rs b/components/layout_2020/fragment_tree/hoisted_shared_fragment.rs
index 0b67d981d34..4d3eb1f7265 100644
--- a/components/layout_2020/fragment_tree/hoisted_shared_fragment.rs
+++ b/components/layout_2020/fragment_tree/hoisted_shared_fragment.rs
@@ -3,7 +3,6 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use app_units::Au;
-use serde::Serialize;
 use style::logical_geometry::WritingMode;
 use style::values::specified::align::AlignFlags;
 
@@ -13,7 +12,6 @@ use crate::geom::{LogicalVec2, PhysicalRect, PhysicalVec};
 /// A reference to a Fragment which is shared between `HoistedAbsolutelyPositionedBox`
 /// and its placeholder `AbsoluteOrFixedPositionedFragment` in the original tree position.
 /// This will be used later in order to paint this hoisted box in tree order.
-#[derive(Serialize)]
 pub(crate) struct HoistedSharedFragment {
     pub fragment: Option<Fragment>,
     /// The "static-position rect" of this absolutely positioned box. This is defined by the
diff --git a/components/layout_2020/fragment_tree/positioning_fragment.rs b/components/layout_2020/fragment_tree/positioning_fragment.rs
index 36b51aa3d2a..b2e6c0ebfd3 100644
--- a/components/layout_2020/fragment_tree/positioning_fragment.rs
+++ b/components/layout_2020/fragment_tree/positioning_fragment.rs
@@ -4,7 +4,6 @@
 
 use app_units::Au;
 use base::print_tree::PrintTree;
-use serde::Serialize;
 use servo_arc::Arc as ServoArc;
 use style::properties::ComputedValues;
 
@@ -15,7 +14,6 @@ use crate::geom::PhysicalRect;
 /// Can contain child fragments with relative coordinates, but does not contribute to painting
 /// itself. [`PositioningFragment`]s may be completely anonymous, or just non-painting Fragments
 /// generated by boxes.
-#[derive(Serialize)]
 pub(crate) struct PositioningFragment {
     pub base: BaseFragment,
     pub rect: PhysicalRect<Au>,
@@ -24,7 +22,6 @@ pub(crate) struct PositioningFragment {
     pub scrollable_overflow: PhysicalRect<Au>,
 
     /// If this fragment was created with a style, the style of the fragment.
-    #[serde(skip_serializing)]
     pub style: Option<ServoArc<ComputedValues>>,
 }
 
diff --git a/components/layout_2020/geom.rs b/components/layout_2020/geom.rs
index 2cc7ae434bf..ce6b969b1ef 100644
--- a/components/layout_2020/geom.rs
+++ b/components/layout_2020/geom.rs
@@ -8,7 +8,6 @@ use std::fmt;
 use std::ops::{Add, AddAssign, Neg, Sub, SubAssign};
 
 use app_units::Au;
-use serde::Serialize;
 use style::logical_geometry::{BlockFlowDirection, InlineBaseDirection, WritingMode};
 use style::values::computed::{
     CSSPixelLength, LengthPercentage, MaxSize as StyleMaxSize, Size as StyleSize,
@@ -29,19 +28,19 @@ pub type PhysicalSides<U> = euclid::SideOffsets2D<U, CSSPixel>;
 pub type AuOrAuto = AutoOr<Au>;
 pub type LengthPercentageOrAuto<'a> = AutoOr<&'a LengthPercentage>;
 
-#[derive(Clone, Copy, PartialEq, Serialize)]
+#[derive(Clone, Copy, PartialEq)]
 pub struct LogicalVec2<T> {
     pub inline: T,
     pub block: T,
 }
 
-#[derive(Clone, Copy, Serialize)]
+#[derive(Clone, Copy)]
 pub struct LogicalRect<T> {
     pub start_corner: LogicalVec2<T>,
     pub size: LogicalVec2<T>,
 }
 
-#[derive(Clone, Copy, Debug, Serialize)]
+#[derive(Clone, Copy, Debug)]
 pub struct LogicalSides<T> {
     pub inline_start: T,
     pub inline_end: T,
@@ -817,7 +816,7 @@ impl Size<Au> {
 
 /// Represents the sizing constraint that the preferred, min and max sizing properties
 /// impose on one axis.
-#[derive(Clone, Copy, Debug, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub(crate) enum SizeConstraint {
     /// Represents a definite preferred size, clamped by minimum and maximum sizes (if any).
     Definite(Au),
diff --git a/components/layout_2020/layout_box_base.rs b/components/layout_2020/layout_box_base.rs
index 8eed9f87d18..4bd2e9c83af 100644
--- a/components/layout_2020/layout_box_base.rs
+++ b/components/layout_2020/layout_box_base.rs
@@ -3,7 +3,6 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use atomic_refcell::AtomicRefCell;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::properties::ComputedValues;
 
@@ -19,12 +18,10 @@ use crate::ConstraintSpace;
 /// passes.
 ///
 /// In the future, this will hold layout results to support incremental layout.
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct LayoutBoxBase {
     pub base_fragment_info: BaseFragmentInfo,
-    #[serde(skip_serializing)]
     pub style: Arc<ComputedValues>,
-    #[serde(skip_serializing)]
     pub cached_inline_content_size:
         AtomicRefCell<Option<(SizeConstraint, InlineContentSizesResult)>>,
 }
diff --git a/components/layout_2020/layout_debug.rs b/components/layout_2020/layout_debug.rs
deleted file mode 100644
index 811254279fb..00000000000
--- a/components/layout_2020/layout_debug.rs
+++ /dev/null
@@ -1,184 +0,0 @@
-/* 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/. */
-
-//! Supports writing a trace file created during each layout scope
-//! that can be viewed by an external tool to make layout debugging easier.
-
-use std::cell::RefCell;
-use std::fs;
-#[cfg(debug_assertions)]
-use std::sync::atomic::{AtomicUsize, Ordering};
-use std::sync::Arc;
-
-#[cfg(not(debug_assertions))]
-use serde::ser::Serializer;
-use serde::Serialize;
-use serde_json::{to_string, to_value, Value};
-
-use crate::flow::BoxTree;
-use crate::fragment_tree::FragmentTree;
-
-thread_local!(static STATE_KEY: RefCell<Option<State>> = const { RefCell::new(None) });
-
-#[cfg(debug_assertions)]
-static DEBUG_ID_COUNTER: AtomicUsize = AtomicUsize::new(0);
-
-pub struct Scope;
-
-#[macro_export]
-macro_rules! layout_debug_scope(
-    ($($arg:tt)*) => (
-        if cfg!(debug_assertions) {
-            layout_debug::Scope::new(format!($($arg)*))
-        } else {
-            layout_debug::Scope
-        }
-    )
-);
-
-#[derive(Serialize)]
-struct TreeValues {
-    pub box_tree: Value,
-    pub fragment_tree: Value,
-}
-
-#[derive(Serialize)]
-struct ScopeData {
-    name: String,
-    pre: TreeValues,
-    post: TreeValues,
-    children: Vec<ScopeData>,
-}
-
-impl ScopeData {
-    fn new(name: String, box_tree: Value, fragment_tree: Value) -> ScopeData {
-        ScopeData {
-            name,
-            pre: TreeValues {
-                box_tree,
-                fragment_tree,
-            },
-            post: TreeValues {
-                box_tree: Value::Null,
-                fragment_tree: Value::Null,
-            },
-            children: vec![],
-        }
-    }
-}
-
-struct State {
-    fragment_tree: Arc<FragmentTree>,
-    box_tree: Arc<BoxTree>,
-    scope_stack: Vec<ScopeData>,
-}
-
-/// A layout debugging scope. The entire state of the box and fragment trees
-/// will be output at the beginning and end of this scope.
-impl Scope {
-    pub fn new(name: String) -> Scope {
-        STATE_KEY.with(|r| {
-            if let Some(ref mut state) = *r.borrow_mut() {
-                let box_tree = to_value(&state.box_tree).unwrap();
-                let fragment_tree = to_value(&state.fragment_tree).unwrap();
-                let data = Box::new(ScopeData::new(name.clone(), box_tree, fragment_tree));
-                state.scope_stack.push(*data);
-            }
-        });
-        Scope
-    }
-}
-
-#[cfg(debug_assertions)]
-impl Drop for Scope {
-    fn drop(&mut self) {
-        STATE_KEY.with(|r| {
-            if let Some(ref mut state) = *r.borrow_mut() {
-                let mut current_scope = state.scope_stack.pop().unwrap();
-                current_scope.post = TreeValues {
-                    box_tree: to_value(&state.box_tree).unwrap(),
-                    fragment_tree: to_value(&state.fragment_tree).unwrap(),
-                };
-                let previous_scope = state.scope_stack.last_mut().unwrap();
-                previous_scope.children.push(current_scope);
-            }
-        });
-    }
-}
-
-/// Begin a layout debug trace. If this has not been called,
-/// creating debug scopes has no effect.
-pub fn begin_trace(box_tree: Arc<BoxTree>, fragment_tree: Arc<FragmentTree>) {
-    assert!(STATE_KEY.with(|r| r.borrow().is_none()));
-
-    STATE_KEY.with(|r| {
-        let box_tree_value = to_value(&box_tree).unwrap();
-        let fragment_tree_value = to_value(&fragment_tree).unwrap();
-        let state = State {
-            scope_stack: vec![*Box::new(ScopeData::new(
-                "root".to_owned(),
-                box_tree_value,
-                fragment_tree_value,
-            ))],
-            box_tree,
-            fragment_tree,
-        };
-        *r.borrow_mut() = Some(state);
-    });
-}
-
-/// End the debug layout trace. This will write the layout
-/// trace to disk in the current directory. The output
-/// file can then be viewed with an external tool.
-pub fn end_trace(generation: u32) {
-    let mut thread_state = STATE_KEY.with(|r| r.borrow_mut().take().unwrap());
-    assert_eq!(thread_state.scope_stack.len(), 1);
-    let mut root_scope = thread_state.scope_stack.pop().unwrap();
-    root_scope.post = TreeValues {
-        box_tree: to_value(&thread_state.box_tree).unwrap_or(Value::Null),
-        fragment_tree: to_value(&thread_state.fragment_tree).unwrap_or(Value::Null),
-    };
-    let result = to_string(&root_scope).unwrap();
-    fs::write(
-        format!("layout_trace-{}.json", generation),
-        result.as_bytes(),
-    )
-    .unwrap();
-}
-
-#[cfg(not(debug_assertions))]
-#[derive(Clone, Debug)]
-pub struct DebugId;
-
-#[cfg(debug_assertions)]
-#[derive(Clone, Debug, Serialize)]
-#[serde(transparent)]
-pub struct DebugId(u16);
-
-#[cfg(not(debug_assertions))]
-impl DebugId {
-    pub fn new() -> DebugId {
-        DebugId
-    }
-}
-
-#[cfg(debug_assertions)]
-impl DebugId {
-    pub fn new() -> DebugId {
-        DebugId(DEBUG_ID_COUNTER.fetch_add(1, Ordering::SeqCst) as u16)
-    }
-}
-
-impl Default for DebugId {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-#[cfg(not(debug_assertions))]
-impl Serialize for DebugId {
-    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
-        serializer.serialize_str(&format!("{:p}", &self))
-    }
-}
diff --git a/components/layout_2020/lib.rs b/components/layout_2020/lib.rs
index e3cfe90cf02..940b95309c8 100644
--- a/components/layout_2020/lib.rs
+++ b/components/layout_2020/lib.rs
@@ -17,7 +17,6 @@ pub mod geom;
 mod layout_box_base;
 mod taffy;
 #[macro_use]
-pub mod layout_debug;
 mod construct_modern;
 mod lists;
 mod positioned;
@@ -32,7 +31,6 @@ use app_units::Au;
 pub use flow::BoxTree;
 pub use fragment_tree::FragmentTree;
 use geom::AuOrAuto;
-use serde::Serialize;
 use style::logical_geometry::WritingMode;
 use style::properties::ComputedValues;
 
@@ -115,7 +113,7 @@ impl<'a> From<&'_ DefiniteContainingBlock<'a>> for IndefiniteContainingBlock {
     }
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct ContainingBlockSize {
     inline: Au,
     block: SizeConstraint,
diff --git a/components/layout_2020/positioned.rs b/components/layout_2020/positioned.rs
index 16905343505..93cb9482500 100644
--- a/components/layout_2020/positioned.rs
+++ b/components/layout_2020/positioned.rs
@@ -7,7 +7,6 @@ use std::mem;
 use app_units::Au;
 use rayon::iter::IntoParallelRefMutIterator;
 use rayon::prelude::{IndexedParallelIterator, ParallelIterator};
-use serde::Serialize;
 use style::computed_values::position::T as Position;
 use style::logical_geometry::WritingMode;
 use style::properties::ComputedValues;
@@ -36,7 +35,7 @@ use crate::{
     ConstraintSpace, ContainingBlock, ContainingBlockSize, DefiniteContainingBlock, SizeConstraint,
 };
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct AbsolutelyPositionedBox {
     pub context: IndependentFormattingContext,
 }
diff --git a/components/layout_2020/replaced.rs b/components/layout_2020/replaced.rs
index 03214f37070..3b0509ba8e3 100644
--- a/components/layout_2020/replaced.rs
+++ b/components/layout_2020/replaced.rs
@@ -15,7 +15,6 @@ use ipc_channel::ipc::{self, IpcSender};
 use net_traits::image_cache::{ImageOrMetadataAvailable, UsePlaceholder};
 use pixels::Image;
 use script_layout_interface::IFrameSize;
-use serde::Serialize;
 use servo_arc::Arc as ServoArc;
 use style::computed_values::object_fit::T as ObjectFit;
 use style::logical_geometry::{Direction, WritingMode};
@@ -36,7 +35,7 @@ use crate::sizing::{ComputeInlineContentSizes, ContentSizes, InlineContentSizesR
 use crate::style_ext::{AspectRatio, Clamp, ComputedValuesExt, ContentBoxSizesAndPBM};
 use crate::{ConstraintSpace, ContainingBlock, SizeConstraint};
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct ReplacedContents {
     pub kind: ReplacedContentKind,
     natural_size: NaturalSizes,
@@ -60,7 +59,7 @@ pub(crate) struct ReplacedContents {
 ///
 /// * IFrames do not have natural width and height or natural ratio according
 ///   to <https://drafts.csswg.org/css-images/#intrinsic-dimensions>.
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct NaturalSizes {
     pub width: Option<Au>,
     pub height: Option<Au>,
@@ -94,7 +93,6 @@ impl NaturalSizes {
     }
 }
 
-#[derive(Serialize)]
 pub(crate) enum CanvasSource {
     WebGL(ImageKey),
     Image(Arc<Mutex<IpcSender<CanvasMsg>>>),
@@ -118,24 +116,24 @@ impl fmt::Debug for CanvasSource {
     }
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct CanvasInfo {
     pub source: CanvasSource,
     pub canvas_id: CanvasId,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct IFrameInfo {
     pub pipeline_id: PipelineId,
     pub browsing_context_id: BrowsingContextId,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct VideoInfo {
     pub image_key: webrender_api::ImageKey,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum ReplacedContentKind {
     Image(Option<Arc<Image>>),
     IFrame(IFrameInfo),
@@ -368,7 +366,6 @@ impl ReplacedContents {
                     base: self.base_fragment_info.into(),
                     style: style.clone(),
                     pipeline_id: iframe.pipeline_id,
-                    browsing_context_id: iframe.browsing_context_id,
                     rect,
                 }))]
             },
diff --git a/components/layout_2020/sizing.rs b/components/layout_2020/sizing.rs
index 46eda7ccbde..e363279540c 100644
--- a/components/layout_2020/sizing.rs
+++ b/components/layout_2020/sizing.rs
@@ -8,7 +8,6 @@ use std::cell::LazyCell;
 use std::ops::{Add, AddAssign};
 
 use app_units::Au;
-use serde::Serialize;
 use style::properties::ComputedValues;
 use style::values::computed::LengthPercentage;
 use style::Zero;
@@ -34,7 +33,7 @@ pub(crate) enum IntrinsicSizingMode {
     Size,
 }
 
-#[derive(Clone, Copy, Debug, Default, Serialize)]
+#[derive(Clone, Copy, Debug, Default)]
 pub(crate) struct ContentSizes {
     pub min_content: Au,
     pub max_content: Au,
@@ -257,7 +256,7 @@ pub(crate) fn outer_inline(
     }
 }
 
-#[derive(Clone, Copy, Debug, Serialize)]
+#[derive(Clone, Copy, Debug)]
 pub(crate) struct InlineContentSizesResult {
     pub sizes: ContentSizes,
     pub depends_on_block_constraints: bool,
diff --git a/components/layout_2020/table/mod.rs b/components/layout_2020/table/mod.rs
index 9e37a42ea4e..147c5285fc1 100644
--- a/components/layout_2020/table/mod.rs
+++ b/components/layout_2020/table/mod.rs
@@ -73,7 +73,6 @@ use std::ops::Range;
 pub(crate) use construct::AnonymousTableContent;
 pub use construct::TableBuilder;
 use euclid::{Point2D, Size2D, UnknownUnit, Vector2D};
-use serde::Serialize;
 use servo_arc::Arc;
 use style::properties::style_structs::Font;
 use style::properties::ComputedValues;
@@ -90,17 +89,15 @@ use crate::style_ext::BorderStyleColor;
 
 pub type TableSize = Size2D<usize, UnknownUnit>;
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub struct Table {
     /// The style of this table. These are the properties that apply to the "wrapper" ie the element
     /// that contains both the grid and the captions. Not all properties are actually used on the
     /// wrapper though, such as background and borders, which apply to the grid.
-    #[serde(skip_serializing)]
     style: Arc<ComputedValues>,
 
     /// The style of this table's grid. This is an anonymous style based on the table's style, but
     /// eliminating all the properties handled by the "wrapper."
-    #[serde(skip_serializing)]
     grid_style: Arc<ComputedValues>,
 
     /// The [`BaseFragmentInfo`] for this table's grid. This is necessary so that when the
@@ -190,7 +187,7 @@ impl Table {
 type TableSlotCoordinates = Point2D<usize, UnknownUnit>;
 pub type TableSlotOffset = Vector2D<usize, UnknownUnit>;
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub struct TableSlotCell {
     /// The [`LayoutBoxBase`] of this table cell.
     base: LayoutBoxBase,
@@ -228,7 +225,6 @@ impl TableSlotCell {
     }
 }
 
-#[derive(Serialize)]
 /// A single table slot. It may be an actual cell, or a reference
 /// to a previous cell that is spanned here
 ///
@@ -269,13 +265,12 @@ impl TableSlot {
 }
 
 /// A row or column of a table.
-#[derive(Clone, Debug, Serialize)]
+#[derive(Clone, Debug)]
 pub struct TableTrack {
     /// The [`BaseFragmentInfo`] of this cell.
     base_fragment_info: BaseFragmentInfo,
 
     /// The style of this table column.
-    #[serde(skip_serializing)]
     style: Arc<ComputedValues>,
 
     /// The index of the table row or column group parent in the table's list of row or column
@@ -287,7 +282,7 @@ pub struct TableTrack {
     is_anonymous: bool,
 }
 
-#[derive(Debug, PartialEq, Serialize)]
+#[derive(Debug, PartialEq)]
 pub enum TableTrackGroupType {
     HeaderGroup,
     FooterGroup,
@@ -295,13 +290,12 @@ pub enum TableTrackGroupType {
     ColumnGroup,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub struct TableTrackGroup {
     /// The [`BaseFragmentInfo`] of this [`TableTrackGroup`].
     base_fragment_info: BaseFragmentInfo,
 
     /// The style of this [`TableTrackGroup`].
-    #[serde(skip_serializing)]
     style: Arc<ComputedValues>,
 
     /// The type of this [`TableTrackGroup`].
@@ -317,7 +311,7 @@ impl TableTrackGroup {
     }
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub struct TableCaption {
     /// The contents of this cell, with its own layout.
     context: ArcRefCell<IndependentFormattingContext>,
diff --git a/components/layout_2020/taffy/mod.rs b/components/layout_2020/taffy/mod.rs
index 6e8446506f9..6aed847e094 100644
--- a/components/layout_2020/taffy/mod.rs
+++ b/components/layout_2020/taffy/mod.rs
@@ -6,7 +6,6 @@ mod stylo_taffy;
 use std::fmt;
 
 use app_units::Au;
-use serde::Serialize;
 use servo_arc::Arc;
 use style::properties::ComputedValues;
 use style::values::computed::TextDecorationLine;
@@ -21,10 +20,9 @@ use crate::formatting_contexts::IndependentFormattingContext;
 use crate::fragment_tree::Fragment;
 use crate::positioned::{AbsolutelyPositionedBox, PositioningContext};
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) struct TaffyContainer {
     children: Vec<ArcRefCell<TaffyItemBox>>,
-    #[serde(skip_serializing)]
     style: Arc<ComputedValues>,
 }
 
@@ -72,18 +70,15 @@ impl TaffyContainer {
     }
 }
 
-#[derive(Serialize)]
 pub(crate) struct TaffyItemBox {
     pub(crate) taffy_layout: taffy::Layout,
     pub(crate) child_fragments: Vec<Fragment>,
-    #[serde(skip_serializing)]
     pub(crate) positioning_context: PositioningContext,
-    #[serde(skip_serializing)]
     pub(crate) style: Arc<ComputedValues>,
     pub(crate) taffy_level_box: TaffyItemBoxInner,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug)]
 pub(crate) enum TaffyItemBoxInner {
     InFlowBox(IndependentFormattingContext),
     OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 962d807d068..6a4635e05e0 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -45,7 +45,7 @@ use layout::traversal::{
     RecalcStyleAndConstructFlows,
 };
 use layout::wrapper::ThreadSafeLayoutNodeHelpers;
-use layout::{layout_debug, layout_debug_scope, parallel, sequential};
+use layout::{parallel, sequential};
 use log::{debug, error, trace};
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use metrics::{PaintTimeMetrics, ProfilerMetadataFactory};
@@ -687,7 +687,6 @@ impl LayoutThread {
     /// benchmarked against those two. It is marked `#[inline(never)]` to aid profiling.
     #[inline(never)]
     fn solve_constraints(layout_root: &mut dyn Flow, layout_context: &LayoutContext) {
-        let _scope = layout_debug_scope!("solve_constraints");
         sequential::reflow(layout_root, layout_context, RelayoutMode::Incremental);
     }
 
@@ -703,8 +702,6 @@ impl LayoutThread {
         time_profiler_chan: profile_time::ProfilerChan,
         layout_context: &LayoutContext,
     ) {
-        let _scope = layout_debug_scope!("solve_constraints_parallel");
-
         // NOTE: this currently computes borders, so any pruning should separate that
         // operation out.
         parallel::reflow(
@@ -1136,10 +1133,6 @@ impl LayoutThread {
             },
         );
 
-        if self.debug.trace_layout {
-            layout_debug::begin_trace(root_flow.clone());
-        }
-
         // Resolve generated content.
         time_profile!(
             profile_time::ProfilerCategory::LayoutGeneratedContent,
@@ -1214,10 +1207,6 @@ impl LayoutThread {
             &mut *layout_context,
         );
 
-        if self.debug.trace_layout {
-            layout_debug::end_trace(self.generation.get());
-        }
-
         if self.debug.dump_flow_tree {
             root_flow.print("Post layout flow tree".to_owned());
         }
diff --git a/components/layout_thread_2020/lib.rs b/components/layout_thread_2020/lib.rs
index fbd862dd6ec..7c689ec7cc3 100644
--- a/components/layout_thread_2020/lib.rs
+++ b/components/layout_thread_2020/lib.rs
@@ -34,7 +34,7 @@ use layout::query::{
     process_resolved_font_style_query, process_resolved_style_request, process_text_index_request,
 };
 use layout::traversal::RecalcStyle;
-use layout::{layout_debug, BoxTree, FragmentTree};
+use layout::{BoxTree, FragmentTree};
 use log::{debug, error};
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use metrics::{PaintTimeMetrics, ProfilerMetadataFactory};
@@ -857,12 +857,6 @@ impl LayoutThread {
             &fragment_tree,
         );
 
-        if self.debug.trace_layout {
-            if let Some(box_tree) = &*self.box_tree.borrow() {
-                layout_debug::begin_trace(box_tree.clone(), fragment_tree.clone());
-            }
-        }
-
         if !reflow_goal.needs_display_list() {
             return;
         }
@@ -926,10 +920,6 @@ impl LayoutThread {
                 .remove_unused_font_resources(keys, instance_keys)
         }
 
-        if self.debug.trace_layout {
-            layout_debug::end_trace(self.generation.get());
-        }
-
         self.generation.set(self.generation.get() + 1);
     }
 
diff --git a/ports/servoshell/prefs.rs b/ports/servoshell/prefs.rs
index 870926bf871..8fc4d1424ef 100644
--- a/ports/servoshell/prefs.rs
+++ b/ports/servoshell/prefs.rs
@@ -394,7 +394,7 @@ pub(crate) fn parse_command_line_arguments(args: Vec<String>) -> ArgumentParsing
             .unwrap_or_else(|err| args_fail(&format!("Error parsing option: -m ({})", err)))
     });
 
-    let mut layout_threads: Option<usize> = opt_match.opt_str("y").map(|layout_threads_str| {
+    let layout_threads: Option<usize> = opt_match.opt_str("y").map(|layout_threads_str| {
         layout_threads_str
             .parse()
             .unwrap_or_else(|err| args_fail(&format!("Error parsing option: -y ({})", err)))
@@ -425,10 +425,6 @@ pub(crate) fn parse_command_line_arguments(args: Vec<String>) -> ArgumentParsing
                 })
             });
 
-    if debug_options.trace_layout {
-        layout_threads = Some(1);
-    }
-
     if opt_match.opt_present("devtools") {
         let port = opt_match
             .opt_str("devtools")