From 2cfe4de09b8efeeb5c60d718db5fb494769c6fdd Mon Sep 17 00:00:00 2001
From: Bobby Holley <bobbyholley@gmail.com>
Date: Tue, 24 Nov 2015 11:25:49 -0800
Subject: [PATCH 1/4] Constrain the ConcreteLayoutFoo associated types to
 provide full tri-ality among the types.

Otherwise we end up with this problem: http://is.gd/ACBLAU
---
 components/layout/wrapper.rs | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/components/layout/wrapper.rs b/components/layout/wrapper.rs
index 828d9bf778d..b26bd79d95d 100644
--- a/components/layout/wrapper.rs
+++ b/components/layout/wrapper.rs
@@ -75,8 +75,10 @@ use util::str::{is_whitespace, search_index};
 /// only ever see these and must never see instances of `LayoutJS`.
 
 pub trait LayoutNode<'ln> : Sized + Copy + Clone {
-    type ConcreteLayoutElement: LayoutElement<'ln>;
-    type ConcreteLayoutDocument: LayoutDocument<'ln>;
+    type ConcreteLayoutElement: LayoutElement<'ln, ConcreteLayoutNode = Self,
+                                              ConcreteLayoutDocument = Self::ConcreteLayoutDocument>;
+    type ConcreteLayoutDocument: LayoutDocument<'ln, ConcreteLayoutNode = Self,
+                                                ConcreteLayoutElement = Self::ConcreteLayoutElement>;
 
     /// Returns the type ID of this node.
     fn type_id(&self) -> NodeTypeId;
@@ -162,8 +164,10 @@ pub trait LayoutNode<'ln> : Sized + Copy + Clone {
 }
 
 pub trait LayoutDocument<'ld> : Sized + Copy + Clone {
-    type ConcreteLayoutNode: LayoutNode<'ld>;
-    type ConcreteLayoutElement: LayoutElement<'ld>;
+    type ConcreteLayoutNode: LayoutNode<'ld, ConcreteLayoutElement = Self::ConcreteLayoutElement,
+                                        ConcreteLayoutDocument = Self>;
+    type ConcreteLayoutElement: LayoutElement<'ld, ConcreteLayoutNode = Self::ConcreteLayoutNode,
+                                              ConcreteLayoutDocument = Self>;
 
     fn as_node(&self) -> Self::ConcreteLayoutNode;
 
@@ -173,8 +177,10 @@ pub trait LayoutDocument<'ld> : Sized + Copy + Clone {
 }
 
 pub trait LayoutElement<'le> : Sized + Copy + Clone + ::selectors::Element + TElementAttributes {
-    type ConcreteLayoutNode: LayoutNode<'le>;
-    type ConcreteLayoutDocument: LayoutDocument<'le>;
+    type ConcreteLayoutNode: LayoutNode<'le, ConcreteLayoutElement = Self,
+                                        ConcreteLayoutDocument = Self::ConcreteLayoutDocument>;
+    type ConcreteLayoutDocument: LayoutDocument<'le, ConcreteLayoutNode = Self::ConcreteLayoutNode,
+                                                ConcreteLayoutElement = Self>;
 
     fn as_node(&self) -> Self::ConcreteLayoutNode;
 
@@ -799,7 +805,7 @@ impl<T> PseudoElementType<T> {
 /// node does not allow any parents or siblings of nodes to be accessed, to avoid races.
 
 pub trait ThreadSafeLayoutNode<'ln> : Clone + Copy + Sized {
-    type ConcreteThreadSafeLayoutElement: ThreadSafeLayoutElement<'ln>;
+    type ConcreteThreadSafeLayoutElement: ThreadSafeLayoutElement<'ln, ConcreteThreadSafeLayoutNode = Self>;
 
     /// Converts self into an `OpaqueNode`.
     fn opaque(&self) -> OpaqueNode;
@@ -947,8 +953,8 @@ trait DangerousThreadSafeLayoutNode<'ln> : ThreadSafeLayoutNode<'ln> {
     unsafe fn dangerous_next_sibling(&self) -> Option<Self>;
 }
 
-pub trait ThreadSafeLayoutElement<'le> {
-    type ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'le>;
+pub trait ThreadSafeLayoutElement<'le>: Clone + Copy + Sized {
+    type ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'le, ConcreteThreadSafeLayoutElement = Self>;
 
     #[inline]
     fn get_attr(&self, namespace: &Namespace, name: &Atom) -> Option<&'le str>;
@@ -1258,6 +1264,7 @@ impl<'ln, ConcreteNode> Iterator for ThreadSafeLayoutNodeChildrenIterator<'ln, C
 
 /// A wrapper around elements that ensures layout can only ever access safe properties and cannot
 /// race on elements.
+#[derive(Copy, Clone)]
 pub struct ServoThreadSafeLayoutElement<'le> {
     element: &'le Element,
 }

From 3aeaff35deb012860fa7afa5861cc76b6c4098bb Mon Sep 17 00:00:00 2001
From: Bobby Holley <bobbyholley@gmail.com>
Date: Tue, 24 Nov 2015 15:02:15 -0800
Subject: [PATCH 2/4] Switch ChildrenIterator to be an associated type.

If we use ThreadsafeLayoutNodeChildrenIterator directly as the return type of children(),
we need to export the DangerousThreadSafeLayoutNode which the iterator implementation
relies upon.
---
 components/layout/wrapper.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/components/layout/wrapper.rs b/components/layout/wrapper.rs
index b26bd79d95d..0a31ccfc429 100644
--- a/components/layout/wrapper.rs
+++ b/components/layout/wrapper.rs
@@ -806,6 +806,7 @@ impl<T> PseudoElementType<T> {
 
 pub trait ThreadSafeLayoutNode<'ln> : Clone + Copy + Sized {
     type ConcreteThreadSafeLayoutElement: ThreadSafeLayoutElement<'ln, ConcreteThreadSafeLayoutNode = Self>;
+    type ChildrenIterator: Iterator<Item = Self> + Sized;
 
     /// Converts self into an `OpaqueNode`.
     fn opaque(&self) -> OpaqueNode;
@@ -819,7 +820,7 @@ pub trait ThreadSafeLayoutNode<'ln> : Clone + Copy + Sized {
     fn flow_debug_id(self) -> usize;
 
     /// Returns an iterator over this node's children.
-    fn children(&self) -> ThreadSafeLayoutNodeChildrenIterator<'ln, Self>;
+    fn children(&self) -> Self::ChildrenIterator;
 
     /// If this is an element, accesses the element data. Fails if this is not an element node.
     #[inline]
@@ -1022,6 +1023,7 @@ impl<'ln> ServoThreadSafeLayoutNode<'ln> {
 
 impl<'ln> ThreadSafeLayoutNode<'ln> for ServoThreadSafeLayoutNode<'ln> {
     type ConcreteThreadSafeLayoutElement = ServoThreadSafeLayoutElement<'ln>;
+    type ChildrenIterator = ThreadSafeLayoutNodeChildrenIterator<'ln, Self>;
 
     fn opaque(&self) -> OpaqueNode {
         OpaqueNodeMethods::from_jsmanaged(unsafe { self.get_jsmanaged() })
@@ -1043,7 +1045,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> for ServoThreadSafeLayoutNode<'ln> {
         self.node.flow_debug_id()
     }
 
-    fn children(&self) -> ThreadSafeLayoutNodeChildrenIterator<'ln, Self> {
+    fn children(&self) -> Self::ChildrenIterator {
         ThreadSafeLayoutNodeChildrenIterator::new(*self)
     }
 

From 77a80919967446639141321ba83b3b0b6d1d1665 Mon Sep 17 00:00:00 2001
From: Bobby Holley <bobbyholley@gmail.com>
Date: Thu, 19 Nov 2015 11:12:44 -0800
Subject: [PATCH 3/4] Generalize css/matching.rs to operate on generic Layout*.

---
 components/layout/css/matching.rs | 45 ++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/components/layout/css/matching.rs b/components/layout/css/matching.rs
index 83d17463712..cebb9463495 100644
--- a/components/layout/css/matching.rs
+++ b/components/layout/css/matching.rs
@@ -32,7 +32,7 @@ use util::arc_ptr_eq;
 use util::cache::{LRUCache, SimpleHashCache};
 use util::opts;
 use util::vec::ForgetfulSink;
-use wrapper::{LayoutElement, LayoutNode, ServoLayoutElement, ServoLayoutNode};
+use wrapper::{LayoutElement, LayoutNode};
 
 pub struct ApplicableDeclarations {
     pub normal: SmallVec<[DeclarationBlock; 16]>,
@@ -161,7 +161,7 @@ pub struct StyleSharingCandidateCache {
     cache: LRUCache<StyleSharingCandidate, ()>,
 }
 
-fn create_common_style_affecting_attributes_from_element(element: &ServoLayoutElement)
+fn create_common_style_affecting_attributes_from_element<'le, E: LayoutElement<'le>>(element: &E)
                                                          -> CommonStyleAffectingAttributes {
     let mut flags = CommonStyleAffectingAttributes::empty();
     for attribute_info in &common_style_affecting_attributes() {
@@ -212,7 +212,7 @@ impl StyleSharingCandidate {
     /// Attempts to create a style sharing candidate from this node. Returns
     /// the style sharing candidate or `None` if this node is ineligible for
     /// style sharing.
-    fn new(element: &ServoLayoutElement) -> Option<StyleSharingCandidate> {
+    fn new<'le, E: LayoutElement<'le>>(element: &E) -> Option<StyleSharingCandidate> {
         let parent_element = match element.parent_element() {
             None => return None,
             Some(parent_element) => parent_element,
@@ -254,11 +254,11 @@ impl StyleSharingCandidate {
             link: element.is_link(),
             namespace: (*element.get_namespace()).clone(),
             common_style_affecting_attributes:
-                   create_common_style_affecting_attributes_from_element(&element)
+                   create_common_style_affecting_attributes_from_element::<'le, E>(&element)
         })
     }
 
-    fn can_share_style_with(&self, element: &ServoLayoutElement) -> bool {
+    fn can_share_style_with<'a, E: LayoutElement<'a>>(&self, element: &E) -> bool {
         if *element.get_local_name() != self.local_name {
             return false
         }
@@ -343,7 +343,7 @@ impl StyleSharingCandidateCache {
         self.cache.iter()
     }
 
-    pub fn insert_if_possible(&mut self, element: &ServoLayoutElement) {
+    pub fn insert_if_possible<'le, E: LayoutElement<'le>>(&mut self, element: &E) {
         match StyleSharingCandidate::new(element) {
             None => {}
             Some(candidate) => self.cache.insert(candidate, ())
@@ -364,7 +364,7 @@ pub enum StyleSharingResult {
     StyleWasShared(usize, RestyleDamage),
 }
 
-pub trait ElementMatchMethods {
+pub trait ElementMatchMethods<'le, ConcreteLayoutElement: LayoutElement<'le>> {
     fn match_element(&self,
                      stylist: &Stylist,
                      parent_bf: Option<&BloomFilter>,
@@ -377,11 +377,11 @@ pub trait ElementMatchMethods {
     unsafe fn share_style_if_possible(&self,
                                       style_sharing_candidate_cache:
                                         &mut StyleSharingCandidateCache,
-                                      parent: Option<ServoLayoutNode>)
+                                      parent: Option<ConcreteLayoutElement::ConcreteLayoutNode>)
                                       -> StyleSharingResult;
 }
 
-pub trait MatchMethods {
+pub trait MatchMethods<'ln, ConcreteLayoutNode: LayoutNode<'ln>> {
     /// Inserts and removes the matching `Descendant` selectors from a bloom
     /// filter. This is used to speed up CSS selector matching to remove
     /// unnecessary tree climbs for `Descendant` queries.
@@ -397,7 +397,7 @@ pub trait MatchMethods {
 
     unsafe fn cascade_node(&self,
                            layout_context: &SharedLayoutContext,
-                           parent: Option<ServoLayoutNode>,
+                           parent: Option<ConcreteLayoutNode>,
                            applicable_declarations: &ApplicableDeclarations,
                            applicable_declarations_cache: &mut ApplicableDeclarationsCache,
                            new_animations_sender: &Mutex<Sender<Animation>>);
@@ -421,14 +421,15 @@ trait PrivateMatchMethods {
                                      -> bool;
 }
 
-trait PrivateElementMatchMethods {
+trait PrivateElementMatchMethods<'le, ConcreteLayoutElement: LayoutElement<'le>> {
     fn share_style_with_candidate_if_possible(&self,
-                                              parent_node: Option<ServoLayoutNode>,
+                                              parent_node: Option<ConcreteLayoutElement::ConcreteLayoutNode>,
                                               candidate: &StyleSharingCandidate)
                                               -> Option<Arc<ComputedValues>>;
 }
 
-impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
+impl<'ln, ConcreteLayoutNode> PrivateMatchMethods for ConcreteLayoutNode
+                                                  where ConcreteLayoutNode: LayoutNode<'ln> {
     fn cascade_node_pseudo_element(&self,
                                    layout_context: &SharedLayoutContext,
                                    parent_style: Option<&Arc<ComputedValues>>,
@@ -547,9 +548,11 @@ impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
     }
 }
 
-impl<'ln> PrivateElementMatchMethods for ServoLayoutElement<'ln> {
+impl<'le, ConcreteLayoutElement> PrivateElementMatchMethods<'le, ConcreteLayoutElement>
+                                 for ConcreteLayoutElement
+                                 where ConcreteLayoutElement: LayoutElement<'le> {
     fn share_style_with_candidate_if_possible(&self,
-                                              parent_node: Option<ServoLayoutNode>,
+                                              parent_node: Option<ConcreteLayoutElement::ConcreteLayoutNode>,
                                               candidate: &StyleSharingCandidate)
                                               -> Option<Arc<ComputedValues>> {
         let parent_node = match parent_node {
@@ -582,7 +585,9 @@ impl<'ln> PrivateElementMatchMethods for ServoLayoutElement<'ln> {
     }
 }
 
-impl<'ln> ElementMatchMethods for ServoLayoutElement<'ln> {
+impl<'le, ConcreteLayoutElement> ElementMatchMethods<'le, ConcreteLayoutElement>
+                                 for ConcreteLayoutElement
+                                 where ConcreteLayoutElement: LayoutElement<'le> {
     fn match_element(&self,
                      stylist: &Stylist,
                      parent_bf: Option<&BloomFilter>,
@@ -615,7 +620,7 @@ impl<'ln> ElementMatchMethods for ServoLayoutElement<'ln> {
     unsafe fn share_style_if_possible(&self,
                                       style_sharing_candidate_cache:
                                         &mut StyleSharingCandidateCache,
-                                      parent: Option<ServoLayoutNode>)
+                                      parent: Option<ConcreteLayoutElement::ConcreteLayoutNode>)
                                       -> StyleSharingResult {
         if opts::get().disable_share_style_cache {
             return StyleSharingResult::CannotShare
@@ -648,7 +653,9 @@ impl<'ln> ElementMatchMethods for ServoLayoutElement<'ln> {
     }
 }
 
-impl<'ln> MatchMethods for ServoLayoutNode<'ln> {
+impl<'ln, ConcreteLayoutNode> MatchMethods<'ln, ConcreteLayoutNode>
+                              for ConcreteLayoutNode
+                              where ConcreteLayoutNode: LayoutNode<'ln> {
     // The below two functions are copy+paste because I can't figure out how to
     // write a function which takes a generic function. I don't think it can
     // be done.
@@ -690,7 +697,7 @@ impl<'ln> MatchMethods for ServoLayoutNode<'ln> {
 
     unsafe fn cascade_node(&self,
                            layout_context: &SharedLayoutContext,
-                           parent: Option<ServoLayoutNode>,
+                           parent: Option<ConcreteLayoutNode>,
                            applicable_declarations: &ApplicableDeclarations,
                            applicable_declarations_cache: &mut ApplicableDeclarationsCache,
                            new_animations_sender: &Mutex<Sender<Animation>>) {

From cf33f00018c7dc44a09086d6bb68b253153635ae Mon Sep 17 00:00:00 2001
From: Bobby Holley <bobbyholley@gmail.com>
Date: Fri, 20 Nov 2015 09:51:05 -0800
Subject: [PATCH 4/4] Generalize the rest of layout to operate on generic
 Layout*.

There wasn't a good way to split this up, unfortunately.

With this change, the only remaining usage of the Servo-specific structures is
in layout_task, where the root node is received from the script task. \o/
---
 components/layout/construct.rs   | 87 ++++++++++++++++++--------------
 components/layout/flow.rs        |  6 +--
 components/layout/fragment.rs    | 26 +++++-----
 components/layout/layout_task.rs |  4 +-
 components/layout/parallel.rs    | 65 +++++++++++++++---------
 components/layout/query.rs       | 41 +++++++--------
 components/layout/sequential.rs  | 14 +++--
 components/layout/table_cell.rs  |  8 ++-
 components/layout/traversal.rs   | 60 ++++++++++++----------
 components/layout/wrapper.rs     | 43 ++++++++++------
 10 files changed, 198 insertions(+), 156 deletions(-)

diff --git a/components/layout/construct.rs b/components/layout/construct.rs
index 53b2416ee8d..49cc3567d57 100644
--- a/components/layout/construct.rs
+++ b/components/layout/construct.rs
@@ -38,6 +38,7 @@ use script::dom::bindings::inheritance::{HTMLElementTypeId, NodeTypeId};
 use script::dom::htmlobjectelement::is_image_data;
 use std::borrow::ToOwned;
 use std::collections::LinkedList;
+use std::marker::PhantomData;
 use std::mem;
 use std::sync::Arc;
 use std::sync::atomic::Ordering;
@@ -57,7 +58,7 @@ use traversal::PostorderNodeMutTraversal;
 use url::Url;
 use util::linked_list;
 use util::opts;
-use wrapper::{PseudoElementType, ServoThreadSafeLayoutNode, TextContent, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
+use wrapper::{PseudoElementType, TextContent, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
 
 /// The results of flow construction for a DOM node.
 #[derive(Clone)]
@@ -208,7 +209,8 @@ impl InlineFragmentsAccumulator {
         }
     }
 
-    fn from_inline_node(node: &ServoThreadSafeLayoutNode) -> InlineFragmentsAccumulator {
+    fn from_inline_node<'ln, N>(node: &N) -> InlineFragmentsAccumulator
+            where N: ThreadSafeLayoutNode<'ln> {
         InlineFragmentsAccumulator {
             fragments: IntermediateInlineFragments::new(),
             enclosing_node: Some(InlineFragmentNodeInfo {
@@ -265,29 +267,35 @@ impl InlineFragmentsAccumulator {
 }
 
 /// An object that knows how to create flows.
-pub struct FlowConstructor<'a> {
+pub struct FlowConstructor<'a, 'ln, N: ThreadSafeLayoutNode<'ln>> {
     /// The layout context.
     pub layout_context: &'a LayoutContext<'a>,
+    /// Satisfy the compiler about the unused parameters, which we use to improve the ergonomics of
+    /// the ensuing impl {} by removing the need to parameterize all the methods individually.
+    phantom1: PhantomData<&'ln ()>,
+    phantom2: PhantomData<N>,
 }
 
-impl<'a> FlowConstructor<'a> {
+impl<'a, 'ln, ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'ln>>
+  FlowConstructor<'a, 'ln, ConcreteThreadSafeLayoutNode> {
     /// Creates a new flow constructor.
-    pub fn new<'b>(layout_context: &'b LayoutContext<'b>)
-                   -> FlowConstructor<'b> {
+    pub fn new(layout_context: &'a LayoutContext<'a>) -> Self {
         FlowConstructor {
             layout_context: layout_context,
+            phantom1: PhantomData,
+            phantom2: PhantomData,
         }
     }
 
     #[inline]
     fn set_flow_construction_result(&self,
-                                    node: &ServoThreadSafeLayoutNode,
+                                    node: &ConcreteThreadSafeLayoutNode,
                                     result: ConstructionResult) {
         node.set_flow_construction_result(result);
     }
 
     /// Builds the fragment for the given block or subclass thereof.
-    fn build_fragment_for_block(&mut self, node: &ServoThreadSafeLayoutNode) -> Fragment {
+    fn build_fragment_for_block(&mut self, node: &ConcreteThreadSafeLayoutNode) -> Fragment {
         let specific_fragment_info = match node.type_id() {
             Some(NodeTypeId::Element(ElementTypeId::HTMLElement(
                         HTMLElementTypeId::HTMLIFrameElement))) => {
@@ -343,7 +351,7 @@ impl<'a> FlowConstructor<'a> {
     fn generate_anonymous_table_flows_if_necessary(&mut self,
                                                    flow: &mut FlowRef,
                                                    child: &mut FlowRef,
-                                                   child_node: &ServoThreadSafeLayoutNode) {
+                                                   child_node: &ConcreteThreadSafeLayoutNode) {
         if !flow.is_block_flow() {
             return
         }
@@ -401,7 +409,7 @@ impl<'a> FlowConstructor<'a> {
                                               flow: &mut FlowRef,
                                               flow_list: &mut Vec<FlowRef>,
                                               absolute_descendants: &mut AbsoluteDescendants,
-                                              node: &ServoThreadSafeLayoutNode) {
+                                              node: &ConcreteThreadSafeLayoutNode) {
         let mut fragments = fragment_accumulator.to_intermediate_inline_fragments();
         if fragments.is_empty() {
             return
@@ -486,8 +494,8 @@ impl<'a> FlowConstructor<'a> {
             &mut self,
             flow: &mut FlowRef,
             consecutive_siblings: &mut Vec<FlowRef>,
-            node: &ServoThreadSafeLayoutNode,
-            kid: ServoThreadSafeLayoutNode,
+            node: &ConcreteThreadSafeLayoutNode,
+            kid: ConcreteThreadSafeLayoutNode,
             inline_fragment_accumulator: &mut InlineFragmentsAccumulator,
             abs_descendants: &mut AbsoluteDescendants) {
         match kid.swap_out_construction_result() {
@@ -595,7 +603,7 @@ impl<'a> FlowConstructor<'a> {
     fn build_flow_for_block_starting_with_fragments(
             &mut self,
             mut flow: FlowRef,
-            node: &ServoThreadSafeLayoutNode,
+            node: &ConcreteThreadSafeLayoutNode,
             initial_fragments: IntermediateInlineFragments)
             -> ConstructionResult {
         // Gather up fragments for the inline flows we might need to create.
@@ -662,7 +670,7 @@ impl<'a> FlowConstructor<'a> {
     ///
     /// FIXME(pcwalton): It is not clear to me that there isn't a cleaner way to handle
     /// `<textarea>`.
-    fn build_flow_for_block_like(&mut self, flow: FlowRef, node: &ServoThreadSafeLayoutNode)
+    fn build_flow_for_block_like(&mut self, flow: FlowRef, node: &ConcreteThreadSafeLayoutNode)
                             -> ConstructionResult {
         let mut initial_fragments = IntermediateInlineFragments::new();
         let node_is_input_or_text_area =
@@ -695,7 +703,7 @@ impl<'a> FlowConstructor<'a> {
     /// Pushes fragments appropriate for the content of the given node onto the given list.
     fn create_fragments_for_node_text_content(&self,
                                               fragments: &mut IntermediateInlineFragments,
-                                              node: &ServoThreadSafeLayoutNode,
+                                              node: &ConcreteThreadSafeLayoutNode,
                                               style: &Arc<ComputedValues>) {
         // Fast path: If there is no text content, return immediately.
         let text_content = node.text_content();
@@ -744,7 +752,7 @@ impl<'a> FlowConstructor<'a> {
     /// Builds a flow for a node with `display: block`. This yields a `BlockFlow` with possibly
     /// other `BlockFlow`s or `InlineFlow`s underneath it, depending on whether {ib} splits needed
     /// to happen.
-    fn build_flow_for_block(&mut self, node: &ServoThreadSafeLayoutNode, float_kind: Option<FloatKind>)
+    fn build_flow_for_block(&mut self, node: &ConcreteThreadSafeLayoutNode, float_kind: Option<FloatKind>)
                             -> ConstructionResult {
         let fragment = self.build_fragment_for_block(node);
         let flow: FlowRef = if node.style().is_multicol() {
@@ -758,7 +766,7 @@ impl<'a> FlowConstructor<'a> {
     /// Bubbles up {ib} splits.
     fn accumulate_inline_block_splits(&mut self,
                                       splits: LinkedList<InlineBlockSplit>,
-                                      node: &ServoThreadSafeLayoutNode,
+                                      node: &ConcreteThreadSafeLayoutNode,
                                       fragment_accumulator: &mut InlineFragmentsAccumulator,
                                       opt_inline_block_splits: &mut LinkedList<InlineBlockSplit>) {
         for split in splits {
@@ -783,7 +791,7 @@ impl<'a> FlowConstructor<'a> {
     /// Returns the `InlineFragmentsConstructionResult`, if any. There will be no
     /// `InlineFragmentsConstructionResult` if this node consisted entirely of ignorable
     /// whitespace.
-    fn build_fragments_for_nonreplaced_inline_content(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_fragments_for_nonreplaced_inline_content(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                                       -> ConstructionResult {
         let mut opt_inline_block_splits: LinkedList<InlineBlockSplit> = LinkedList::new();
         let mut fragment_accumulator = InlineFragmentsAccumulator::from_inline_node(node);
@@ -897,7 +905,7 @@ impl<'a> FlowConstructor<'a> {
     /// Creates an `InlineFragmentsConstructionResult` for replaced content. Replaced content
     /// doesn't render its children, so this just nukes a child's fragments and creates a
     /// `Fragment`.
-    fn build_fragments_for_replaced_inline_content(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_fragments_for_replaced_inline_content(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                                    -> ConstructionResult {
         for kid in node.children() {
             self.set_flow_construction_result(&kid, ConstructionResult::None)
@@ -941,7 +949,7 @@ impl<'a> FlowConstructor<'a> {
         ConstructionResult::ConstructionItem(construction_item)
     }
 
-    fn build_fragment_for_inline_block(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_fragment_for_inline_block(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                        -> ConstructionResult {
         let block_flow_result = self.build_flow_for_block(node, None);
         let (block_flow, abs_descendants) = match block_flow_result {
@@ -973,7 +981,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// This is an annoying case, because the computed `display` value is `block`, but the
     /// hypothetical box is inline.
-    fn build_fragment_for_absolutely_positioned_inline(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_fragment_for_absolutely_positioned_inline(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                                        -> ConstructionResult {
         let block_flow_result = self.build_flow_for_block(node, None);
         let (block_flow, abs_descendants) = match block_flow_result {
@@ -1005,7 +1013,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds one or more fragments for a node with `display: inline`. This yields an
     /// `InlineFragmentsConstructionResult`.
-    fn build_fragments_for_inline(&mut self, node: &ServoThreadSafeLayoutNode) -> ConstructionResult {
+    fn build_fragments_for_inline(&mut self, node: &ConcreteThreadSafeLayoutNode) -> ConstructionResult {
         // Is this node replaced content?
         if !node.is_replaced_content() {
             // Go to a path that concatenates our kids' fragments.
@@ -1021,7 +1029,7 @@ impl<'a> FlowConstructor<'a> {
     /// `caption-side` property is equal to the given `side`.
     fn place_table_caption_under_table_wrapper_on_side(&mut self,
                                                        table_wrapper_flow: &mut FlowRef,
-                                                       node: &ServoThreadSafeLayoutNode,
+                                                       node: &ConcreteThreadSafeLayoutNode,
                                                        side: caption_side::T) {
         // Only flows that are table captions are matched here.
         for kid in node.children() {
@@ -1046,7 +1054,7 @@ impl<'a> FlowConstructor<'a> {
     fn generate_anonymous_missing_child(&mut self,
                                         child_flows: Vec<FlowRef>,
                                         flow: &mut FlowRef,
-                                        node: &ServoThreadSafeLayoutNode) {
+                                        node: &ConcreteThreadSafeLayoutNode) {
         let mut anonymous_flow = flow.generate_missing_child_flow(node);
         let mut consecutive_siblings = vec!();
         for kid_flow in child_flows {
@@ -1072,7 +1080,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: table`. This yields a `TableWrapperFlow` with
     /// possibly other `TableCaptionFlow`s or `TableFlow`s underneath it.
-    fn build_flow_for_table_wrapper(&mut self, node: &ServoThreadSafeLayoutNode, float_value: float::T)
+    fn build_flow_for_table_wrapper(&mut self, node: &ConcreteThreadSafeLayoutNode, float_value: float::T)
                                     -> ConstructionResult {
         let fragment = Fragment::new(node, SpecificFragmentInfo::TableWrapper);
         let mut wrapper_flow: FlowRef = Arc::new(
@@ -1134,7 +1142,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: table-caption`. This yields a `TableCaptionFlow`
     /// with possibly other `BlockFlow`s or `InlineFlow`s underneath it.
-    fn build_flow_for_table_caption(&mut self, node: &ServoThreadSafeLayoutNode) -> ConstructionResult {
+    fn build_flow_for_table_caption(&mut self, node: &ConcreteThreadSafeLayoutNode) -> ConstructionResult {
         let fragment = self.build_fragment_for_block(node);
         let flow = Arc::new(TableCaptionFlow::from_fragment(fragment));
         self.build_flow_for_block_like(flow, node)
@@ -1142,7 +1150,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: table-row-group`. This yields a `TableRowGroupFlow`
     /// with possibly other `TableRowFlow`s underneath it.
-    fn build_flow_for_table_rowgroup(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_flow_for_table_rowgroup(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                      -> ConstructionResult {
         let fragment = Fragment::new(node, SpecificFragmentInfo::TableRow);
         let flow = Arc::new(TableRowGroupFlow::from_fragment(fragment));
@@ -1151,7 +1159,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: table-row`. This yields a `TableRowFlow` with
     /// possibly other `TableCellFlow`s underneath it.
-    fn build_flow_for_table_row(&mut self, node: &ServoThreadSafeLayoutNode) -> ConstructionResult {
+    fn build_flow_for_table_row(&mut self, node: &ConcreteThreadSafeLayoutNode) -> ConstructionResult {
         let fragment = Fragment::new(node, SpecificFragmentInfo::TableRow);
         let flow = Arc::new(TableRowFlow::from_fragment(fragment));
         self.build_flow_for_block_like(flow, node)
@@ -1159,7 +1167,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: table-cell`. This yields a `TableCellFlow` with
     /// possibly other `BlockFlow`s or `InlineFlow`s underneath it.
-    fn build_flow_for_table_cell(&mut self, node: &ServoThreadSafeLayoutNode) -> ConstructionResult {
+    fn build_flow_for_table_cell(&mut self, node: &ConcreteThreadSafeLayoutNode) -> ConstructionResult {
         let fragment = Fragment::new(node, SpecificFragmentInfo::TableCell);
 
         // Determine if the table cell should be hidden. Per CSS 2.1 § 17.6.1.1, this will be true
@@ -1180,7 +1188,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: list-item`. This yields a `ListItemFlow` with
     /// possibly other `BlockFlow`s or `InlineFlow`s underneath it.
-    fn build_flow_for_list_item(&mut self, node: &ServoThreadSafeLayoutNode, flotation: float::T)
+    fn build_flow_for_list_item(&mut self, node: &ConcreteThreadSafeLayoutNode, flotation: float::T)
                                 -> ConstructionResult {
         let flotation = FloatKind::from_property(flotation);
         let marker_fragments = match node.style().get_list().list_style_image.0 {
@@ -1239,7 +1247,7 @@ impl<'a> FlowConstructor<'a> {
     }
 
     /// Creates a fragment for a node with `display: table-column`.
-    fn build_fragments_for_table_column(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_fragments_for_table_column(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                         -> ConstructionResult {
         // CSS 2.1 § 17.2.1. Treat all child fragments of a `table-column` as `display: none`.
         for kid in node.children() {
@@ -1254,7 +1262,7 @@ impl<'a> FlowConstructor<'a> {
 
     /// Builds a flow for a node with `display: table-column-group`.
     /// This yields a `TableColGroupFlow`.
-    fn build_flow_for_table_colgroup(&mut self, node: &ServoThreadSafeLayoutNode)
+    fn build_flow_for_table_colgroup(&mut self, node: &ConcreteThreadSafeLayoutNode)
                                      -> ConstructionResult {
         let fragment =
             Fragment::new(node,
@@ -1283,7 +1291,7 @@ impl<'a> FlowConstructor<'a> {
     }
 
     /// Builds a flow for a node with 'display: flex'.
-    fn build_flow_for_flex(&mut self, node: &ServoThreadSafeLayoutNode, float_kind: Option<FloatKind>)
+    fn build_flow_for_flex(&mut self, node: &ConcreteThreadSafeLayoutNode, float_kind: Option<FloatKind>)
                            -> ConstructionResult {
         let fragment = self.build_fragment_for_block(node);
         let flow = Arc::new(FlexFlow::from_fragment(fragment, float_kind));
@@ -1295,7 +1303,7 @@ impl<'a> FlowConstructor<'a> {
     ///
     /// TODO(pcwalton): Add some more fast paths, like toggling `display: none`, adding block kids
     /// to block parents with no {ib} splits, adding out-of-flow kids, etc.
-    pub fn repair_if_possible(&mut self, node: &ServoThreadSafeLayoutNode) -> bool {
+    pub fn repair_if_possible(&mut self, node: &ConcreteThreadSafeLayoutNode) -> bool {
         // We can skip reconstructing the flow if we don't have to reconstruct and none of our kids
         // did either.
         //
@@ -1403,14 +1411,16 @@ impl<'a> FlowConstructor<'a> {
     }
 }
 
-impl<'a> PostorderNodeMutTraversal for FlowConstructor<'a> {
+impl<'a, 'ln, ConcreteThreadSafeLayoutNode> PostorderNodeMutTraversal<'ln, ConcreteThreadSafeLayoutNode>
+                                            for FlowConstructor<'a, 'ln, ConcreteThreadSafeLayoutNode>
+                                            where ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'ln> {
     // Construct Flow based on 'display', 'position', and 'float' values.
     //
     // CSS 2.1 Section 9.7
     //
     // TODO: This should actually consult the table in that section to get the
     // final computed value for 'display'.
-    fn process(&mut self, node: &ServoThreadSafeLayoutNode) -> bool {
+    fn process(&mut self, node: &ConcreteThreadSafeLayoutNode) -> bool {
         // Get the `display` property for this node, and determine whether this node is floated.
         let (display, float, positioning) = match node.type_id() {
             None => {
@@ -1580,7 +1590,8 @@ trait NodeUtils {
     fn swap_out_construction_result(self) -> ConstructionResult;
 }
 
-impl<'ln> NodeUtils for ServoThreadSafeLayoutNode<'ln> {
+impl<'ln, ConcreteThreadSafeLayoutNode> NodeUtils for ConcreteThreadSafeLayoutNode
+                                                  where ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'ln> {
     fn is_replaced_content(&self) -> bool {
         match self.type_id() {
             None |
@@ -1639,7 +1650,7 @@ trait ObjectElement<'a> {
     fn object_data(&self) -> Option<Url>;
 }
 
-impl<'ln> ObjectElement<'ln> for ServoThreadSafeLayoutNode<'ln> {
+impl<'ln, N> ObjectElement<'ln> for N  where N: ThreadSafeLayoutNode<'ln> {
     fn get_type_and_data(&self) -> (Option<&'ln str>, Option<&'ln str>) {
         let elem = self.as_element();
         (elem.get_attr(&ns!(), &atom!("type")), elem.get_attr(&ns!(), &atom!("data")))
diff --git a/components/layout/flow.rs b/components/layout/flow.rs
index 80487b7cbb8..3af799fc82e 100644
--- a/components/layout/flow.rs
+++ b/components/layout/flow.rs
@@ -59,7 +59,7 @@ use table_wrapper::TableWrapperFlow;
 use util::geometry::ZERO_RECT;
 use util::logical_geometry::{LogicalRect, LogicalSize, WritingMode};
 use util::print_tree::PrintTree;
-use wrapper::{PseudoElementType, ServoThreadSafeLayoutNode, ThreadSafeLayoutNode};
+use wrapper::{PseudoElementType, ThreadSafeLayoutNode};
 
 /// Virtual methods that make up a float context.
 ///
@@ -435,7 +435,7 @@ pub trait ImmutableFlowUtils {
     fn need_anonymous_flow(self, child: &Flow) -> bool;
 
     /// Generates missing child flow of this flow.
-    fn generate_missing_child_flow(self, node: &ServoThreadSafeLayoutNode) -> FlowRef;
+    fn generate_missing_child_flow<'ln, N: ThreadSafeLayoutNode<'ln>>(self, node: &N) -> FlowRef;
 
     /// Returns true if this flow contains fragments that are roots of an absolute flow tree.
     fn contains_roots_of_absolute_flow_tree(&self) -> bool;
@@ -1212,7 +1212,7 @@ impl<'a> ImmutableFlowUtils for &'a Flow {
     /// FIXME(pcwalton): This duplicates some logic in
     /// `generate_anonymous_table_flows_if_necessary()`. We should remove this function eventually,
     /// as it's harder to understand.
-    fn generate_missing_child_flow(self, node: &ServoThreadSafeLayoutNode) -> FlowRef {
+    fn generate_missing_child_flow<'ln, N: ThreadSafeLayoutNode<'ln>>(self, node: &N) -> FlowRef {
         let mut style = node.style().clone();
         match self.class() {
             FlowClass::Table | FlowClass::TableRowGroup => {
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index 06167c3b59b..5eae8be6891 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -50,7 +50,7 @@ use util::geometry::ZERO_POINT;
 use util::logical_geometry::{LogicalMargin, LogicalRect, LogicalSize, WritingMode};
 use util::range::*;
 use util::str::slice_chars;
-use wrapper::{PseudoElementType, ServoThreadSafeLayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
+use wrapper::{PseudoElementType, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
 
 /// Fragments (`struct Fragment`) are the leaves of the layout tree. They cannot position
 /// themselves. In general, fragments do not have a simple correspondence with CSS fragments in the
@@ -309,7 +309,7 @@ pub struct CanvasFragmentInfo {
 }
 
 impl CanvasFragmentInfo {
-    pub fn new(node: &ServoThreadSafeLayoutNode, data: HTMLCanvasData) -> CanvasFragmentInfo {
+    pub fn new<'ln, N: ThreadSafeLayoutNode<'ln>>(node: &N, data: HTMLCanvasData) -> CanvasFragmentInfo {
         CanvasFragmentInfo {
             replaced_image_fragment_info: ReplacedImageFragmentInfo::new(node,
                 Some(Au::from_px(data.width as i32)),
@@ -345,11 +345,10 @@ impl ImageFragmentInfo {
     ///
     /// FIXME(pcwalton): The fact that image fragments store the cache in the fragment makes little
     /// sense to me.
-    pub fn new(node: &ServoThreadSafeLayoutNode,
-               url: Option<Url>,
-               layout_context: &LayoutContext)
-               -> ImageFragmentInfo {
-        fn convert_length(node: &ServoThreadSafeLayoutNode, name: &Atom) -> Option<Au> {
+    pub fn new<'ln, N: ThreadSafeLayoutNode<'ln>>(node: &N, url: Option<Url>,
+                                                  layout_context: &LayoutContext) -> ImageFragmentInfo {
+        fn convert_length<'ln, N>(node: &N, name: &Atom) -> Option<Au>
+                where N: ThreadSafeLayoutNode<'ln> {
             let element = node.as_element();
             element.get_attr(&ns!(), name)
                    .and_then(|string| string.parse().ok())
@@ -423,9 +422,10 @@ pub struct ReplacedImageFragmentInfo {
 }
 
 impl ReplacedImageFragmentInfo {
-    pub fn new(node: &ServoThreadSafeLayoutNode,
-               dom_width: Option<Au>,
-               dom_height: Option<Au>) -> ReplacedImageFragmentInfo {
+    pub fn new<'ln, N>(node: &N,
+                       dom_width: Option<Au>,
+                       dom_height: Option<Au>) -> ReplacedImageFragmentInfo
+            where N: ThreadSafeLayoutNode<'ln> {
         let is_vertical = node.style().writing_mode.is_vertical();
         ReplacedImageFragmentInfo {
             computed_inline_size: None,
@@ -583,7 +583,7 @@ pub struct IframeFragmentInfo {
 
 impl IframeFragmentInfo {
     /// Creates the information specific to an iframe fragment.
-    pub fn new(node: &ServoThreadSafeLayoutNode) -> IframeFragmentInfo {
+    pub fn new<'ln, N: ThreadSafeLayoutNode<'ln>>(node: &N) -> IframeFragmentInfo {
         let pipeline_id = node.iframe_pipeline_id();
         IframeFragmentInfo {
             pipeline_id: pipeline_id,
@@ -758,7 +758,7 @@ pub struct TableColumnFragmentInfo {
 
 impl TableColumnFragmentInfo {
     /// Create the information specific to an table column fragment.
-    pub fn new(node: &ServoThreadSafeLayoutNode) -> TableColumnFragmentInfo {
+    pub fn new<'ln, N: ThreadSafeLayoutNode<'ln>>(node: &N) -> TableColumnFragmentInfo {
         let element = node.as_element();
         let span = element.get_attr(&ns!(), &atom!("span"))
                           .and_then(|string| string.parse().ok())
@@ -771,7 +771,7 @@ impl TableColumnFragmentInfo {
 
 impl Fragment {
     /// Constructs a new `Fragment` instance.
-    pub fn new(node: &ServoThreadSafeLayoutNode, specific: SpecificFragmentInfo) -> Fragment {
+    pub fn new<'ln, N: ThreadSafeLayoutNode<'ln>>(node: &N, specific: SpecificFragmentInfo) -> Fragment {
         let style = node.style().clone();
         let writing_mode = style.writing_mode;
 
diff --git a/components/layout/layout_task.rs b/components/layout/layout_task.rs
index 9aac21f7a88..cf7ca56da00 100644
--- a/components/layout/layout_task.rs
+++ b/components/layout/layout_task.rs
@@ -758,7 +758,7 @@ impl LayoutTask {
         possibly_locked_rw_data.block(rw_data);
     }
 
-    fn try_get_layout_root(&self, node: ServoLayoutNode) -> Option<FlowRef> {
+    fn try_get_layout_root<'ln, N: LayoutNode<'ln>>(&self, node: N) -> Option<FlowRef> {
         let mut layout_data_ref = node.mutate_layout_data();
         let layout_data =
             match layout_data_ref.as_mut() {
@@ -1271,7 +1271,7 @@ impl LayoutTask {
         }
     }
 
-    unsafe fn dirty_all_nodes(node: ServoLayoutNode) {
+    unsafe fn dirty_all_nodes<'ln, N: LayoutNode<'ln>>(node: N) {
         for node in node.traverse_preorder() {
             // TODO(cgaebel): mark nodes which are sensitive to media queries as
             // "changed":
diff --git a/components/layout/parallel.rs b/components/layout/parallel.rs
index c8549c37eb6..4023ed9fbf3 100644
--- a/components/layout/parallel.rs
+++ b/components/layout/parallel.rs
@@ -22,8 +22,7 @@ use traversal::{ConstructFlows, RecalcStyleForNode};
 use traversal::{PostorderDomTraversal, PreorderDomTraversal};
 use util::opts;
 use util::workqueue::{WorkQueue, WorkUnit, WorkerProxy};
-use wrapper::UnsafeLayoutNode;
-use wrapper::{LayoutNode, ServoLayoutNode, layout_node_from_unsafe_layout_node, layout_node_to_unsafe_layout_node};
+use wrapper::{LayoutNode, UnsafeLayoutNode};
 
 const CHUNK_SIZE: usize = 64;
 
@@ -88,7 +87,9 @@ pub type ChunkedFlowTraversalFunction =
 pub type FlowTraversalFunction = extern "Rust" fn(UnsafeFlow, &SharedLayoutContext);
 
 /// A parallel top-down DOM traversal.
-pub trait ParallelPreorderDomTraversal : PreorderDomTraversal {
+pub trait ParallelPreorderDomTraversal<'ln, ConcreteLayoutNode>
+        : PreorderDomTraversal<'ln, ConcreteLayoutNode>
+          where ConcreteLayoutNode: LayoutNode<'ln> {
     fn run_parallel(&self,
                     nodes: UnsafeLayoutNodeList,
                     proxy: &mut WorkerProxy<SharedLayoutContext, UnsafeLayoutNodeList>);
@@ -103,9 +104,7 @@ pub trait ParallelPreorderDomTraversal : PreorderDomTraversal {
         let mut discovered_child_nodes = Vec::new();
         for unsafe_node in *unsafe_nodes.0 {
             // Get a real layout node.
-            let node: ServoLayoutNode = unsafe {
-                layout_node_from_unsafe_layout_node(&unsafe_node)
-            };
+            let node = unsafe { ConcreteLayoutNode::from_unsafe(&unsafe_node) };
 
             // Perform the appropriate traversal.
             self.process(node);
@@ -123,7 +122,7 @@ pub trait ParallelPreorderDomTraversal : PreorderDomTraversal {
             // Possibly enqueue the children.
             if child_count != 0 {
                 for kid in node.children() {
-                    discovered_child_nodes.push(layout_node_to_unsafe_layout_node(&kid))
+                    discovered_child_nodes.push(kid.to_unsafe())
                 }
             } else {
                 // If there were no more children, start walking back up.
@@ -141,7 +140,9 @@ pub trait ParallelPreorderDomTraversal : PreorderDomTraversal {
 }
 
 /// A parallel bottom-up DOM traversal.
-trait ParallelPostorderDomTraversal : PostorderDomTraversal {
+trait ParallelPostorderDomTraversal<'ln, ConcreteLayoutNode>
+        : PostorderDomTraversal<'ln, ConcreteLayoutNode>
+          where ConcreteLayoutNode: LayoutNode<'ln> {
     fn root(&self) -> OpaqueNode;
 
     /// Process current node and potentially traverse its ancestors.
@@ -157,9 +158,7 @@ trait ParallelPostorderDomTraversal : PostorderDomTraversal {
     /// fetch-and-subtract the parent's children count.
     fn run_parallel(&self, unsafe_node: UnsafeLayoutNode) {
         // Get a real layout node.
-        let mut node: ServoLayoutNode = unsafe {
-            layout_node_from_unsafe_layout_node(&unsafe_node)
-        };
+        let mut node = unsafe { ConcreteLayoutNode::from_unsafe(&unsafe_node) };
         loop {
             // Perform the appropriate operation.
             self.process(node);
@@ -349,41 +348,59 @@ impl<'a> ParallelPreorderFlowTraversal for ComputeAbsolutePositions<'a> {
 
 impl<'a> ParallelPostorderFlowTraversal for BuildDisplayList<'a> {}
 
-impl<'a> ParallelPostorderDomTraversal for ConstructFlows<'a> {
+impl<'a, 'ln, ConcreteLayoutNode> ParallelPostorderDomTraversal<'ln, ConcreteLayoutNode>
+                                  for ConstructFlows<'a>
+                                  where ConcreteLayoutNode: LayoutNode<'ln> {
     fn root(&self) -> OpaqueNode {
         self.root
     }
 }
 
-impl <'a> ParallelPreorderDomTraversal for RecalcStyleForNode<'a> {
+impl<'a, 'ln, ConcreteLayoutNode> ParallelPreorderDomTraversal<'ln, ConcreteLayoutNode>
+                                  for RecalcStyleForNode<'a>
+                                  where ConcreteLayoutNode: LayoutNode<'ln> {
     fn run_parallel(&self,
                     unsafe_nodes: UnsafeLayoutNodeList,
                     proxy: &mut WorkerProxy<SharedLayoutContext, UnsafeLayoutNodeList>) {
-        self.run_parallel_helper(unsafe_nodes, proxy, recalc_style, construct_flows)
+        // Not exactly sure why we need UFCS here, but we seem to.
+        <RecalcStyleForNode<'a> as ParallelPreorderDomTraversal<'ln, ConcreteLayoutNode>>
+          ::run_parallel_helper(self, unsafe_nodes, proxy,
+                                recalc_style::<'ln, ConcreteLayoutNode>,
+                                construct_flows::<'ln, ConcreteLayoutNode>)
     }
 }
 
-fn recalc_style(unsafe_nodes: UnsafeLayoutNodeList,
-                proxy: &mut WorkerProxy<SharedLayoutContext, UnsafeLayoutNodeList>) {
+fn recalc_style<'ln, ConcreteLayoutNode>(unsafe_nodes: UnsafeLayoutNodeList,
+                                         proxy: &mut WorkerProxy<SharedLayoutContext, UnsafeLayoutNodeList>)
+                                         where ConcreteLayoutNode: LayoutNode<'ln> {
     let shared_layout_context = proxy.user_data();
     let layout_context = LayoutContext::new(shared_layout_context);
     let recalc_style_for_node_traversal = RecalcStyleForNode {
         layout_context: &layout_context,
         root: unsafe_nodes.1,
     };
-    recalc_style_for_node_traversal.run_parallel(unsafe_nodes, proxy)
+
+    // The UFCS is necessary here to select the proper set of generic routines which
+    // will eventually cast the UnsafeNode to a concrete LayoutNode implementation.
+    <RecalcStyleForNode as ParallelPreorderDomTraversal<'ln, ConcreteLayoutNode>>
+        ::run_parallel(&recalc_style_for_node_traversal, unsafe_nodes, proxy)
 }
 
-fn construct_flows(root: OpaqueNode,
-                   unsafe_node: UnsafeLayoutNode,
-                   proxy: &mut WorkerProxy<SharedLayoutContext, UnsafeLayoutNodeList>) {
+fn construct_flows<'ln, ConcreteLayoutNode: LayoutNode<'ln>>(
+        root: OpaqueNode,
+        unsafe_node: UnsafeLayoutNode,
+        proxy: &mut WorkerProxy<SharedLayoutContext, UnsafeLayoutNodeList>) {
     let shared_layout_context = proxy.user_data();
     let layout_context = LayoutContext::new(shared_layout_context);
     let construct_flows_traversal = ConstructFlows {
         layout_context: &layout_context,
         root: root,
     };
-    construct_flows_traversal.run_parallel(unsafe_node)
+
+    // The UFCS is necessary here to select the proper set of generic routines which
+    // will eventually cast the UnsafeNode to a concrete LayoutNode implementation.
+    <ConstructFlows as ParallelPostorderDomTraversal<'ln, ConcreteLayoutNode>>
+        ::run_parallel(&construct_flows_traversal, unsafe_node)
 }
 
 fn assign_inline_sizes(unsafe_flows: UnsafeFlowList,
@@ -440,13 +457,13 @@ fn run_queue_with_custom_work_data_type<To, F>(
     queue.run(shared_layout_context);
 }
 
-pub fn traverse_dom_preorder(root: ServoLayoutNode,
+pub fn traverse_dom_preorder<'ln, ConcreteLayoutNode: LayoutNode<'ln>>(root: ConcreteLayoutNode,
                              shared_layout_context: &SharedLayoutContext,
                              queue: &mut WorkQueue<SharedLayoutContext, WorkQueueData>) {
     run_queue_with_custom_work_data_type(queue, |queue| {
         queue.push(WorkUnit {
-            fun:  recalc_style,
-            data: (box vec![layout_node_to_unsafe_layout_node(&root)], root.opaque()),
+            fun:  recalc_style::<'ln, ConcreteLayoutNode>,
+            data: (box vec![root.to_unsafe()], root.opaque()),
         });
     }, shared_layout_context);
 }
diff --git a/components/layout/query.rs b/components/layout/query.rs
index 1a00ffbdb55..076b972061d 100644
--- a/components/layout/query.rs
+++ b/components/layout/query.rs
@@ -31,7 +31,7 @@ use style::values::AuExtensionMethods;
 use util::cursor::Cursor;
 use util::geometry::ZERO_POINT;
 use util::logical_geometry::WritingMode;
-use wrapper::{LayoutNode, ServoLayoutNode, ServoThreadSafeLayoutNode, ThreadSafeLayoutNode};
+use wrapper::{LayoutNode, ThreadSafeLayoutNode};
 
 pub struct LayoutRPCImpl(pub Arc<Mutex<LayoutTaskData>>);
 
@@ -292,9 +292,8 @@ impl FragmentBorderBoxIterator for MarginRetrievingFragmentBorderBoxIterator {
     }
 }
 
-pub fn process_content_box_request(requested_node: ServoLayoutNode,
-                                   layout_root: &mut FlowRef)
-                                   -> Rect<Au> {
+pub fn process_content_box_request<'ln, N: LayoutNode<'ln>>(
+        requested_node: N, layout_root: &mut FlowRef) -> Rect<Au> {
     // FIXME(pcwalton): This has not been updated to handle the stacking context relative
     // stuff. So the position is wrong in most cases.
     let mut iterator = UnioningFragmentBorderBoxIterator::new(requested_node.opaque());
@@ -305,9 +304,8 @@ pub fn process_content_box_request(requested_node: ServoLayoutNode,
     }
 }
 
-pub fn process_content_boxes_request(requested_node: ServoLayoutNode,
-                                     layout_root: &mut FlowRef)
-                                     -> Vec<Rect<Au>> {
+pub fn process_content_boxes_request<'ln, N: LayoutNode<'ln>>(requested_node: N, layout_root: &mut FlowRef)
+        -> Vec<Rect<Au>> {
     // FIXME(pcwalton): This has not been updated to handle the stacking context relative
     // stuff. So the position is wrong in most cases.
     let mut iterator = CollectingFragmentBorderBoxIterator::new(requested_node.opaque());
@@ -431,9 +429,8 @@ impl FragmentBorderBoxIterator for ParentOffsetBorderBoxIterator {
     }
 }
 
-pub fn process_node_geometry_request(requested_node: ServoLayoutNode,
-                                     layout_root: &mut FlowRef)
-                                     -> Rect<i32> {
+pub fn process_node_geometry_request<'ln, N: LayoutNode<'ln>>(requested_node: N, layout_root: &mut FlowRef)
+        -> Rect<i32> {
     let mut iterator = FragmentLocatingFragmentIterator::new(requested_node.opaque());
     sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
     iterator.client_rect
@@ -441,12 +438,10 @@ pub fn process_node_geometry_request(requested_node: ServoLayoutNode,
 
 /// Return the resolved value of property for a given (pseudo)element.
 /// https://drafts.csswg.org/cssom/#resolved-value
-pub fn process_resolved_style_request(requested_node: ServoLayoutNode,
-                                      pseudo: &Option<PseudoElement>,
-                                      property: &Atom,
-                                      layout_root: &mut FlowRef)
-                                      -> Option<String> {
-    let layout_node = ServoThreadSafeLayoutNode::new(&requested_node);
+pub fn process_resolved_style_request<'ln, N: LayoutNode<'ln>>(
+            requested_node: N, pseudo: &Option<PseudoElement>,
+            property: &Atom, layout_root: &mut FlowRef) -> Option<String> {
+    let layout_node = requested_node.to_threadsafe();
     let layout_node = match pseudo {
         &Some(PseudoElement::Before) => layout_node.get_before_pseudo(),
         &Some(PseudoElement::After) => layout_node.get_after_pseudo(),
@@ -480,10 +475,11 @@ pub fn process_resolved_style_request(requested_node: ServoLayoutNode,
     // There are probably other quirks.
     let applies = true;
 
-    fn used_value_for_position_property(layout_node: ServoThreadSafeLayoutNode,
-                                        layout_root: &mut FlowRef,
-                                        requested_node: ServoLayoutNode,
-                                        property: &Atom) -> Option<String> {
+    fn used_value_for_position_property<'ln, N: LayoutNode<'ln>>(
+            layout_node: N::ConcreteThreadSafeLayoutNode,
+            layout_root: &mut FlowRef,
+            requested_node: N,
+            property: &Atom) -> Option<String> {
         let layout_data = layout_node.borrow_layout_data();
         let position = layout_data.as_ref().map(|layout_data| {
             match layout_data.data.flow_construction_result {
@@ -560,9 +556,8 @@ pub fn process_resolved_style_request(requested_node: ServoLayoutNode,
     }
 }
 
-pub fn process_offset_parent_query(requested_node: ServoLayoutNode,
-                                   layout_root: &mut FlowRef)
-                                   -> OffsetParentResponse {
+pub fn process_offset_parent_query<'ln, N: LayoutNode<'ln>>(requested_node: N, layout_root: &mut FlowRef)
+        -> OffsetParentResponse {
     let mut iterator = ParentOffsetBorderBoxIterator::new(requested_node.opaque());
     sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
     let parent_info_index = iterator.parent_nodes.iter().rposition(|info| info.is_some());
diff --git a/components/layout/sequential.rs b/components/layout/sequential.rs
index 36f754a2cf5..275f4ed0429 100644
--- a/components/layout/sequential.rs
+++ b/components/layout/sequential.rs
@@ -19,11 +19,15 @@ use traversal::{BuildDisplayList, ComputeAbsolutePositions};
 use traversal::{PostorderDomTraversal, PreorderDomTraversal};
 use util::geometry::ZERO_POINT;
 use util::opts;
-use wrapper::{LayoutNode, ServoLayoutNode};
+use wrapper::LayoutNode;
 
-pub fn traverse_dom_preorder(root: ServoLayoutNode,
-                             shared_layout_context: &SharedLayoutContext) {
-    fn doit(node: ServoLayoutNode, recalc_style: RecalcStyleForNode, construct_flows: ConstructFlows) {
+pub fn traverse_dom_preorder<'le, N>(root: N,
+                                     shared_layout_context: &SharedLayoutContext)
+                                     where N: LayoutNode<'le> {
+    fn doit<'le, N>(node: N,
+                    recalc_style: RecalcStyleForNode,
+                    construct_flows: ConstructFlows)
+                    where N: LayoutNode<'le> {
         recalc_style.process(node);
 
         for kid in node.children() {
@@ -43,7 +47,7 @@ pub fn traverse_dom_preorder(root: ServoLayoutNode,
         root: root.opaque(),
     };
 
-    doit(root, recalc_style, construct_flows);
+    doit::<'le, N>(root, recalc_style, construct_flows);
 }
 
 pub fn resolve_generated_content(root: &mut FlowRef, shared_layout_context: &SharedLayoutContext) {
diff --git a/components/layout/table_cell.rs b/components/layout/table_cell.rs
index 2b89c693599..ad6d2ca1804 100644
--- a/components/layout/table_cell.rs
+++ b/components/layout/table_cell.rs
@@ -25,7 +25,7 @@ use table::InternalTable;
 use table_row::{CollapsedBorder, CollapsedBorderProvenance};
 use util::logical_geometry::{LogicalMargin, LogicalRect, LogicalSize, WritingMode};
 use util::print_tree::PrintTree;
-use wrapper::{ServoThreadSafeLayoutNode, ThreadSafeLayoutNode};
+use wrapper::{ThreadSafeLayoutNode};
 
 /// A table formatting context.
 #[derive(RustcEncodable)]
@@ -45,10 +45,8 @@ pub struct TableCellFlow {
 }
 
 impl TableCellFlow {
-    pub fn from_node_fragment_and_visibility_flag(node: &ServoThreadSafeLayoutNode,
-                                                  fragment: Fragment,
-                                                  visible: bool)
-                                                  -> TableCellFlow {
+    pub fn from_node_fragment_and_visibility_flag<'ln, N: ThreadSafeLayoutNode<'ln>>(
+            node: &N, fragment: Fragment, visible: bool) -> TableCellFlow {
         TableCellFlow {
             block_flow: BlockFlow::from_fragment(fragment, None),
             collapsed_borders: CollapsedBordersForCell::new(),
diff --git a/components/layout/traversal.rs b/components/layout/traversal.rs
index a224f57feb1..cf3be1b9d94 100644
--- a/components/layout/traversal.rs
+++ b/components/layout/traversal.rs
@@ -17,8 +17,8 @@ use std::cell::RefCell;
 use std::mem;
 use util::opts;
 use util::tid::tid;
-use wrapper::{LayoutNode, ServoLayoutNode, layout_node_to_unsafe_layout_node};
-use wrapper::{ServoThreadSafeLayoutNode, ThreadSafeLayoutNode, UnsafeLayoutNode};
+use wrapper::{LayoutNode, UnsafeLayoutNode};
+use wrapper::{ThreadSafeLayoutNode};
 
 /// Every time we do another layout, the old bloom filters are invalid. This is
 /// detected by ticking a generation number every layout.
@@ -51,10 +51,11 @@ thread_local!(
 ///
 /// If one does not exist, a new one will be made for you. If it is out of date,
 /// it will be cleared and reused.
-fn take_task_local_bloom_filter(parent_node: Option<ServoLayoutNode>,
-                                root: OpaqueNode,
-                                layout_context: &LayoutContext)
-                                -> Box<BloomFilter> {
+fn take_task_local_bloom_filter<'ln, N>(parent_node: Option<N>,
+                                        root: OpaqueNode,
+                                        layout_context: &LayoutContext)
+                                        -> Box<BloomFilter>
+                                        where N: LayoutNode<'ln> {
     STYLE_BLOOM.with(|style_bloom| {
         match (parent_node, style_bloom.borrow_mut().take()) {
             // Root node. Needs new bloom filter.
@@ -70,7 +71,7 @@ fn take_task_local_bloom_filter(parent_node: Option<ServoLayoutNode>,
             }
             // Found cached bloom filter.
             (Some(parent), Some((mut bloom_filter, old_node, old_generation))) => {
-                if old_node == layout_node_to_unsafe_layout_node(&parent) &&
+                if old_node == parent.to_unsafe() &&
                     old_generation == layout_context.shared.generation {
                     // Hey, the cached parent is our parent! We can reuse the bloom filter.
                     debug!("[{}] Parent matches (={}). Reusing bloom filter.", tid(), old_node.0);
@@ -97,9 +98,10 @@ fn put_task_local_bloom_filter(bf: Box<BloomFilter>,
 }
 
 /// "Ancestors" in this context is inclusive of ourselves.
-fn insert_ancestors_into_bloom_filter(bf: &mut Box<BloomFilter>,
-                                      mut n: ServoLayoutNode,
-                                      root: OpaqueNode) {
+fn insert_ancestors_into_bloom_filter<'ln, N>(bf: &mut Box<BloomFilter>,
+                                              mut n: N,
+                                              root: OpaqueNode)
+                                              where N: LayoutNode<'ln> {
     debug!("[{}] Inserting ancestors.", tid());
     let mut ancestors = 0;
     loop {
@@ -116,21 +118,21 @@ fn insert_ancestors_into_bloom_filter(bf: &mut Box<BloomFilter>,
 
 
 /// A top-down traversal.
-pub trait PreorderDomTraversal {
+pub trait PreorderDomTraversal<'ln, ConcreteLayoutNode: LayoutNode<'ln>>  {
     /// The operation to perform. Return true to continue or false to stop.
-    fn process(&self, node: ServoLayoutNode);
+    fn process(&self, node: ConcreteLayoutNode);
 }
 
 /// A bottom-up traversal, with a optional in-order pass.
-pub trait PostorderDomTraversal {
+pub trait PostorderDomTraversal<'ln, ConcreteLayoutNode: LayoutNode<'ln>> {
     /// The operation to perform. Return true to continue or false to stop.
-    fn process(&self, node: ServoLayoutNode);
+    fn process(&self, node: ConcreteLayoutNode);
 }
 
 /// A bottom-up, parallelizable traversal.
-pub trait PostorderNodeMutTraversal {
+pub trait PostorderNodeMutTraversal<'ln, ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'ln>> {
     /// The operation to perform. Return true to continue or false to stop.
-    fn process<'a>(&'a mut self, node: &ServoThreadSafeLayoutNode<'a>) -> bool;
+    fn process(&mut self, node: &ConcreteThreadSafeLayoutNode) -> bool;
 }
 
 /// The recalc-style-for-node traversal, which styles each node and must run before
@@ -141,10 +143,12 @@ pub struct RecalcStyleForNode<'a> {
     pub root: OpaqueNode,
 }
 
-impl<'a> PreorderDomTraversal for RecalcStyleForNode<'a> {
+impl<'a, 'ln, ConcreteLayoutNode> PreorderDomTraversal<'ln, ConcreteLayoutNode>
+                                  for RecalcStyleForNode<'a>
+                                  where ConcreteLayoutNode: LayoutNode<'ln> {
     #[inline]
     #[allow(unsafe_code)]
-    fn process(&self, node: ServoLayoutNode) {
+    fn process(&self, node: ConcreteLayoutNode) {
         // Initialize layout data.
         //
         // FIXME(pcwalton): Stop allocating here. Ideally this should just be done by the HTML
@@ -162,7 +166,7 @@ impl<'a> PreorderDomTraversal for RecalcStyleForNode<'a> {
             // Remove existing CSS styles from nodes whose content has changed (e.g. text changed),
             // to force non-incremental reflow.
             if node.has_changed() {
-                let node = ServoThreadSafeLayoutNode::new(&node);
+                let node = node.to_threadsafe();
                 node.unstyle();
             }
 
@@ -199,7 +203,7 @@ impl<'a> PreorderDomTraversal for RecalcStyleForNode<'a> {
                         },
                         None => {
                             if node.has_changed() {
-                                ServoThreadSafeLayoutNode::new(&node).set_restyle_damage(
+                                node.to_threadsafe().set_restyle_damage(
                                     incremental::rebuild_and_reflow())
                             }
                             None
@@ -222,12 +226,12 @@ impl<'a> PreorderDomTraversal for RecalcStyleForNode<'a> {
                 }
                 StyleSharingResult::StyleWasShared(index, damage) => {
                     style_sharing_candidate_cache.touch(index);
-                    ServoThreadSafeLayoutNode::new(&node).set_restyle_damage(damage);
+                    node.to_threadsafe().set_restyle_damage(damage);
                 }
             }
         }
 
-        let unsafe_layout_node = layout_node_to_unsafe_layout_node(&node);
+        let unsafe_layout_node = node.to_unsafe();
 
         // Before running the children, we need to insert our nodes into the bloom
         // filter.
@@ -246,13 +250,15 @@ pub struct ConstructFlows<'a> {
     pub root: OpaqueNode,
 }
 
-impl<'a> PostorderDomTraversal for ConstructFlows<'a> {
+impl<'a, 'ln, ConcreteLayoutNode> PostorderDomTraversal<'ln, ConcreteLayoutNode>
+                                  for ConstructFlows<'a>
+                                  where ConcreteLayoutNode: LayoutNode<'ln> {
     #[inline]
     #[allow(unsafe_code)]
-    fn process(&self, node: ServoLayoutNode) {
+    fn process(&self, node: ConcreteLayoutNode) {
         // Construct flows for this node.
         {
-            let tnode = ServoThreadSafeLayoutNode::new(&node);
+            let tnode = node.to_threadsafe();
 
             // Always reconstruct if incremental layout is turned off.
             let nonincremental_layout = opts::get().nonincremental_layout;
@@ -277,7 +283,7 @@ impl<'a> PostorderDomTraversal for ConstructFlows<'a> {
             node.set_dirty_descendants(false);
         }
 
-        let unsafe_layout_node = layout_node_to_unsafe_layout_node(&node);
+        let unsafe_layout_node = node.to_unsafe();
 
         let (mut bf, old_node, old_generation) =
             STYLE_BLOOM.with(|style_bloom| {
@@ -296,7 +302,7 @@ impl<'a> PostorderDomTraversal for ConstructFlows<'a> {
             Some(parent) => {
                 // Otherwise, put it back, but remove this node.
                 node.remove_from_bloom_filter(&mut *bf);
-                let unsafe_parent = layout_node_to_unsafe_layout_node(&parent);
+                let unsafe_parent = parent.to_unsafe();
                 put_task_local_bloom_filter(bf, &unsafe_parent, self.layout_context);
             },
         };
diff --git a/components/layout/wrapper.rs b/components/layout/wrapper.rs
index 0a31ccfc429..be9f48703e3 100644
--- a/components/layout/wrapper.rs
+++ b/components/layout/wrapper.rs
@@ -71,15 +71,25 @@ use style::restyle_hints::{ElementSnapshot, RESTYLE_DESCENDANTS, RESTYLE_LATER_S
 use url::Url;
 use util::str::{is_whitespace, search_index};
 
+/// Opaque type stored in type-unsafe work queues for parallel layout.
+/// Must be transmutable to and from LayoutNode.
+pub type UnsafeLayoutNode = (usize, usize);
+
 /// A wrapper so that layout can access only the methods that it should have access to. Layout must
 /// only ever see these and must never see instances of `LayoutJS`.
 
 pub trait LayoutNode<'ln> : Sized + Copy + Clone {
+    type ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'ln>;
     type ConcreteLayoutElement: LayoutElement<'ln, ConcreteLayoutNode = Self,
                                               ConcreteLayoutDocument = Self::ConcreteLayoutDocument>;
     type ConcreteLayoutDocument: LayoutDocument<'ln, ConcreteLayoutNode = Self,
                                                 ConcreteLayoutElement = Self::ConcreteLayoutElement>;
 
+    fn to_unsafe(&self) -> UnsafeLayoutNode;
+    unsafe fn from_unsafe(&UnsafeLayoutNode) -> Self;
+
+    fn to_threadsafe(&self) -> Self::ConcreteThreadSafeLayoutNode;
+
     /// Returns the type ID of this node.
     fn type_id(&self) -> NodeTypeId;
 
@@ -268,9 +278,26 @@ impl<'ln> ServoLayoutNode<'ln> {
 }
 
 impl<'ln> LayoutNode<'ln> for ServoLayoutNode<'ln> {
+    type ConcreteThreadSafeLayoutNode = ServoThreadSafeLayoutNode<'ln>;
     type ConcreteLayoutElement = ServoLayoutElement<'ln>;
     type ConcreteLayoutDocument = ServoLayoutDocument<'ln>;
 
+    fn to_unsafe(&self) -> UnsafeLayoutNode {
+        unsafe {
+            let ptr: usize = mem::transmute_copy(self);
+            (ptr, 0)
+        }
+    }
+
+    unsafe fn from_unsafe(n: &UnsafeLayoutNode) -> Self {
+        let (node, _) = *n;
+        mem::transmute(node)
+    }
+
+    fn to_threadsafe(&self) -> Self::ConcreteThreadSafeLayoutNode {
+        ServoThreadSafeLayoutNode::new(self)
+    }
+
     fn type_id(&self) -> NodeTypeId {
         unsafe {
             self.node.type_id_for_layout()
@@ -1281,22 +1308,6 @@ impl<'le> ThreadSafeLayoutElement<'le> for ServoThreadSafeLayoutElement<'le> {
     }
 }
 
-/// Opaque type stored in type-unsafe work queues for parallel layout.
-/// Must be transmutable to and from LayoutNode.
-pub type UnsafeLayoutNode = (usize, usize);
-
-pub fn layout_node_to_unsafe_layout_node(node: &ServoLayoutNode) -> UnsafeLayoutNode {
-    unsafe {
-        let ptr: usize = mem::transmute_copy(node);
-        (ptr, 0)
-    }
-}
-
-pub unsafe fn layout_node_from_unsafe_layout_node(node: &UnsafeLayoutNode) -> ServoLayoutNode {
-    let (node, _) = *node;
-    mem::transmute(node)
-}
-
 pub enum TextContent {
     Text(String),
     GeneratedContent(Vec<ContentItem>),