script: Move the layout_wrapper outside of script.

This allows us to have ensure_data() and clear_data() functions on the TElement
trait, instead of hacking around it adding methods in random traits.

This also allows us to do some further cleanup, which I'd rather do in a
followup.

Cargo.lock

@@ -1485,11 +1485,13 @@ name = "layout_thread"
 version = "0.0.1"
 dependencies = [
  "app_units 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atomic_refcell 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "euclid 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "gfx 0.0.1",
  "gfx_traits 0.0.1",
  "heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "html5ever 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ipc-channel 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "layout 0.0.1",
  "layout_traits 0.0.1",
@@ -1499,6 +1501,7 @@ dependencies = [
  "net_traits 0.0.1",
  "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "profile_traits 0.0.1",
+ "range 0.0.1",
  "rayon 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "script 0.0.1",
  "script_layout_interface 0.0.1",
@@ -2413,7 +2416,6 @@ version = "0.0.1"
 dependencies = [
  "angle 0.2.0 (git+https://github.com/servo/angle?branch=servo)",
  "app_units 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "atomic_refcell 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "audio-video-metadata 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "base64 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2431,7 +2433,6 @@ dependencies = [
  "encoding 0.2.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "euclid 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "gfx_traits 0.0.1",
  "gleam 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "half 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2458,7 +2459,6 @@ dependencies = [
  "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "profile_traits 0.0.1",
- "range 0.0.1",
  "ref_filter_map 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "ref_slice 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",

components/layout/lib.rs

@@ -14,7 +14,6 @@ extern crate atomic_refcell;
 #[macro_use]
 extern crate bitflags;
 extern crate canvas_traits;
-extern crate core;
 extern crate euclid;
 extern crate fnv;
 extern crate gfx;
@@ -55,7 +54,7 @@ pub mod animation;
 mod block;
 pub mod construct;
 pub mod context;
-mod data;
+pub mod data;
 pub mod display_list_builder;
 mod flex;
 mod floats;

components/layout/traversal.rs

@@ -4,7 +4,6 @@
 
 //! Traversals over the DOM and flow trees, running the layout computations.
 
-use atomic_refcell::AtomicRefCell;
 use construct::FlowConstructor;
 use context::LayoutContext;
 use display_list_builder::DisplayListBuildState;
@@ -13,13 +12,12 @@ use flow::{CAN_BE_FRAGMENTED, Flow, ImmutableFlowUtils, PostorderFlowTraversal};
 use script_layout_interface::wrapper_traits::{LayoutNode, ThreadSafeLayoutNode};
 use servo_config::opts;
 use style::context::{SharedStyleContext, StyleContext};
-use style::data::ElementData;
 use style::dom::{NodeInfo, TElement, TNode};
 use style::selector_parser::RestyleDamage;
 use style::servo::restyle_damage::{BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW, REPAINT};
 use style::traversal::{DomTraversal, TraversalDriver, recalc_style_at};
 use style::traversal::PerLevelTraversalData;
-use wrapper::{GetRawData, LayoutNodeHelpers, LayoutNodeLayoutData};
+use wrapper::{GetRawData, LayoutNodeLayoutData};
 use wrapper::ThreadSafeLayoutNodeHelpers;
 
 pub struct RecalcStyleAndConstructFlows<'a> {
@@ -59,7 +57,7 @@ impl<'a, E> DomTraversal<E> for RecalcStyleAndConstructFlows<'a>
                         context: &mut StyleContext<E>, node: E::ConcreteNode) {
         // FIXME(pcwalton): Stop allocating here. Ideally this should just be
         // done by the HTML parser.
-        node.initialize_data();
+        unsafe { node.initialize_data() };
 
         if !node.is_text_node() {
             let el = node.as_element().unwrap();
@@ -81,15 +79,6 @@ impl<'a, E> DomTraversal<E> for RecalcStyleAndConstructFlows<'a>
         node.parent_node().unwrap().to_threadsafe().restyle_damage() != RestyleDamage::empty()
     }
 
-    unsafe fn ensure_element_data(element: &E) -> &AtomicRefCell<ElementData> {
-        element.as_node().initialize_data();
-        element.get_data().unwrap()
-    }
-
-    unsafe fn clear_element_data(element: &E) {
-        element.as_node().clear_data();
-    }
-
     fn shared_context(&self) -> &SharedStyleContext {
         &self.context.style_context
     }

components/layout/wrapper.rs

@@ -31,21 +31,13 @@
 #![allow(unsafe_code)]
 
 use atomic_refcell::{AtomicRef, AtomicRefMut};
-use core::nonzero::NonZero;
 use data::{LayoutData, LayoutDataFlags, StyleAndLayoutData};
-use script_layout_interface::{OpaqueStyleAndLayoutData, StyleData};
+use script_layout_interface::wrapper_traits::{ThreadSafeLayoutElement, ThreadSafeLayoutNode};
-use script_layout_interface::wrapper_traits::{LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
 use script_layout_interface::wrapper_traits::GetLayoutData;
 use style::computed_values::content::{self, ContentItem};
 use style::dom::{NodeInfo, TNode};
 use style::selector_parser::RestyleDamage;
 
-pub unsafe fn drop_style_and_layout_data(data: OpaqueStyleAndLayoutData) {
-    let ptr: *mut StyleData = data.ptr.get();
-    let non_opaque: *mut StyleAndLayoutData = ptr as *mut _;
-    let _ = Box::from_raw(non_opaque);
-}
-
 pub trait LayoutNodeLayoutData {
     /// Similar to borrow_data*, but returns the full PersistentLayoutData rather
     /// than only the style::data::ElementData.
@@ -81,30 +73,6 @@ impl<T: GetLayoutData> GetRawData for T {
     }
 }
 
-pub trait LayoutNodeHelpers {
-    fn initialize_data(&self);
-    fn clear_data(&self);
-}
-
-impl<T: LayoutNode> LayoutNodeHelpers for T {
-    fn initialize_data(&self) {
-        if self.get_raw_data().is_none() {
-            let ptr: *mut StyleAndLayoutData =
-                Box::into_raw(Box::new(StyleAndLayoutData::new()));
-            let opaque = OpaqueStyleAndLayoutData {
-                ptr: unsafe { NonZero::new(ptr as *mut StyleData) }
-            };
-            unsafe { self.init_style_and_layout_data(opaque) };
-        };
-    }
-
-    fn clear_data(&self) {
-        if self.get_raw_data().is_some() {
-            unsafe { drop_style_and_layout_data(self.take_style_and_layout_data()) };
-        }
-    }
-}
-
 pub trait ThreadSafeLayoutNodeHelpers {
     /// Returns the layout data flags for this node.
     fn flags(self) -> LayoutDataFlags;

components/layout_thread/Cargo.toml

@@ -11,11 +11,13 @@ path = "lib.rs"
 
 [dependencies]
 app_units = "0.5"
+atomic_refcell = "0.1"
 euclid = "0.15"
 fnv = "1.0"
 gfx = {path = "../gfx"}
 gfx_traits = {path = "../gfx_traits"}
 heapsize = "0.4"
+html5ever = "0.18"
 ipc-channel = "0.8"
 layout = {path = "../layout"}
 layout_traits = {path = "../layout_traits"}
@@ -25,6 +27,7 @@ msg = {path = "../msg"}
 net_traits = {path = "../net_traits"}
 parking_lot = {version = "0.4", features = ["nightly"]}
 profile_traits = {path = "../profile_traits"}
+range = {path = "../range"}
 rayon = "0.8"
 script = {path = "../script"}
 script_layout_interface = {path = "../script_layout_interface"}

components/layout_thread/dom_wrapper.rs

@@ -30,21 +30,22 @@
 
 #![allow(unsafe_code)]
 
-use atomic_refcell::{AtomicRef, AtomicRefCell};
+use atomic_refcell::{AtomicRef, AtomicRefMut, AtomicRefCell};
-use dom::bindings::inheritance::{CharacterDataTypeId, ElementTypeId};
+use core::nonzero::NonZero;
-use dom::bindings::inheritance::{HTMLElementTypeId, NodeTypeId};
-use dom::bindings::js::LayoutJS;
-use dom::characterdata::LayoutCharacterDataHelpers;
-use dom::document::{Document, LayoutDocumentHelpers, PendingRestyle};
-use dom::element::{Element, LayoutElementHelpers, RawLayoutElementHelpers};
-use dom::node::{CAN_BE_FRAGMENTED, DIRTY_ON_VIEWPORT_SIZE_CHANGE, HAS_DIRTY_DESCENDANTS, IS_IN_DOC};
-use dom::node::{HANDLED_SNAPSHOT, HAS_SNAPSHOT};
-use dom::node::{LayoutNodeHelpers, Node};
-use dom::text::Text;
 use gfx_traits::ByteIndex;
 use html5ever::{LocalName, Namespace};
+use layout::data::StyleAndLayoutData;
+use layout::wrapper::GetRawData;
 use msg::constellation_msg::{BrowsingContextId, PipelineId};
 use range::Range;
+use script::layout_exports::{CAN_BE_FRAGMENTED, DIRTY_ON_VIEWPORT_SIZE_CHANGE, HAS_DIRTY_DESCENDANTS, IS_IN_DOC};
+use script::layout_exports::{CharacterDataTypeId, ElementTypeId, HTMLElementTypeId, NodeTypeId};
+use script::layout_exports::{Document, Element, Node, Text};
+use script::layout_exports::{HANDLED_SNAPSHOT, HAS_SNAPSHOT};
+use script::layout_exports::{LayoutCharacterDataHelpers, LayoutDocumentHelpers};
+use script::layout_exports::{LayoutElementHelpers, LayoutNodeHelpers, RawLayoutElementHelpers};
+use script::layout_exports::LayoutJS;
+use script::layout_exports::PendingRestyle;
 use script_layout_interface::{HTMLCanvasData, LayoutNodeType, SVGSVGData, TrustedNodeAddress};
 use script_layout_interface::{OpaqueStyleAndLayoutData, StyleData};
 use script_layout_interface::wrapper_traits::{DangerousThreadSafeLayoutNode, GetLayoutData, LayoutNode};
@@ -79,6 +80,12 @@ use style::shared_lock::{SharedRwLock as StyleSharedRwLock, Locked as StyleLocke
 use style::str::is_whitespace;
 use style::stylearc::Arc;
 
+pub unsafe fn drop_style_and_layout_data(data: OpaqueStyleAndLayoutData) {
+    let ptr: *mut StyleData = data.ptr.get();
+    let non_opaque: *mut StyleAndLayoutData = ptr as *mut _;
+    let _ = Box::from_raw(non_opaque);
+}
+
 #[derive(Copy, Clone)]
 pub struct ServoLayoutNode<'a> {
     /// The wrapped node.
@@ -244,6 +251,17 @@ impl<'ln> LayoutNode for ServoLayoutNode<'ln> {
         self.script_type_id().into()
     }
 
+    unsafe fn initialize_data(&self) {
+        if self.get_raw_data().is_none() {
+            let ptr: *mut StyleAndLayoutData =
+                Box::into_raw(Box::new(StyleAndLayoutData::new()));
+            let opaque = OpaqueStyleAndLayoutData {
+                ptr: NonZero::new(ptr as *mut StyleData),
+            };
+            self.init_style_and_layout_data(opaque);
+        };
+    }
+
     unsafe fn init_style_and_layout_data(&self, data: OpaqueStyleAndLayoutData) {
         self.get_jsmanaged().init_style_and_layout_data(data);
     }
@@ -477,6 +495,17 @@ impl<'le> TElement for ServoLayoutElement<'le> {
         old_value - 1
     }
 
+    unsafe fn clear_data(&self) {
+        if self.get_raw_data().is_some() {
+            drop_style_and_layout_data(self.as_node().take_style_and_layout_data());
+        }
+    }
+
+    unsafe fn ensure_data(&self) -> AtomicRefMut<ElementData> {
+        self.as_node().initialize_data();
+        self.mutate_data().unwrap()
+    }
+
     fn get_data(&self) -> Option<&AtomicRefCell<ElementData>> {
         unsafe {
             self.get_style_and_layout_data().map(|d| {

components/layout_thread/lib.rs

@@ -7,13 +7,18 @@
 
 #![feature(box_syntax)]
 #![feature(mpsc_select)]
+#![feature(nonzero)]
 
 extern crate app_units;
+extern crate atomic_refcell;
+extern crate core;
 extern crate euclid;
 extern crate fnv;
 extern crate gfx;
 extern crate gfx_traits;
 extern crate heapsize;
+#[macro_use]
+extern crate html5ever;
 extern crate ipc_channel;
 #[macro_use]
 extern crate layout;
@@ -27,6 +32,7 @@ extern crate net_traits;
 extern crate parking_lot;
 #[macro_use]
 extern crate profile_traits;
+extern crate range;
 extern crate rayon;
 extern crate script;
 extern crate script_layout_interface;
@@ -40,7 +46,11 @@ extern crate servo_url;
 extern crate style;
 extern crate webrender_api;
 
+mod dom_wrapper;
+
 use app_units::Au;
+use dom_wrapper::{ServoLayoutElement, ServoLayoutDocument, ServoLayoutNode};
+use dom_wrapper::drop_style_and_layout_data;
 use euclid::{Point2D, Rect, Size2D, ScaleFactor};
 use fnv::FnvHashMap;
 use gfx::display_list::{OpaqueNode, WebRenderImageInfo};
@@ -71,7 +81,6 @@ use layout::sequential;
 use layout::traversal::{ComputeAbsolutePositions, RecalcStyleAndConstructFlows};
 use layout::webrender_helpers::WebRenderDisplayListConverter;
 use layout::wrapper::LayoutNodeLayoutData;
-use layout::wrapper::drop_style_and_layout_data;
 use layout_traits::LayoutThreadFactory;
 use msg::constellation_msg::PipelineId;
 use msg::constellation_msg::TopLevelBrowsingContextId;
@@ -80,7 +89,6 @@ use parking_lot::RwLock;
 use profile_traits::mem::{self, Report, ReportKind, ReportsChan};
 use profile_traits::time::{self, TimerMetadata, profile};
 use profile_traits::time::{TimerMetadataFrameType, TimerMetadataReflowType};
-use script::layout_wrapper::{ServoLayoutElement, ServoLayoutDocument, ServoLayoutNode};
 use script_layout_interface::message::{Msg, NewLayoutThreadInfo, Reflow, ReflowQueryType};
 use script_layout_interface::message::{ScriptReflow, ReflowComplete};
 use script_layout_interface::rpc::{LayoutRPC, MarginStyleResponse, NodeOverflowResponse, OffsetParentResponse};

components/script/Cargo.toml

@@ -27,7 +27,6 @@ tinyfiledialogs = "2.5.9"
 angle = {git = "https://github.com/servo/angle", branch = "servo"}
 app_units = "0.5"
 audio-video-metadata = "0.1.2"
-atomic_refcell = "0.1"
 base64 = "0.5.2"
 bitflags = "0.7"
 bluetooth_traits = {path = "../bluetooth_traits"}
@@ -44,7 +43,6 @@ encoding = "0.2"
 euclid = "0.15"
 fnv = "1.0"
 gleam = "0.4"
-gfx_traits = {path = "../gfx_traits"}
 half = "1.0"
 heapsize = "0.4"
 heapsize_derive = "0.1"
@@ -68,7 +66,6 @@ open = "1.1.1"
 parking_lot = "0.4"
 phf = "0.7.18"
 profile_traits = {path = "../profile_traits"}
-range = {path = "../range"}
 ref_filter_map = "1.0.1"
 ref_slice = "1.0"
 regex = "0.2"

components/script/lib.rs

@@ -26,7 +26,6 @@
 
 extern crate angle;
 extern crate app_units;
-extern crate atomic_refcell;
 extern crate audio_video_metadata;
 extern crate base64;
 #[macro_use]
@@ -46,7 +45,6 @@ extern crate domobject_derive;
 extern crate encoding;
 extern crate euclid;
 extern crate fnv;
-extern crate gfx_traits;
 extern crate gleam;
 extern crate half;
 #[macro_use] extern crate heapsize;
@@ -78,7 +76,6 @@ extern crate parking_lot;
 extern crate phf;
 #[macro_use]
 extern crate profile_traits;
-extern crate range;
 extern crate ref_filter_map;
 extern crate ref_slice;
 extern crate regex;
@@ -115,7 +112,6 @@ pub mod document_loader;
 mod dom;
 pub mod fetch;
 mod layout_image;
-pub mod layout_wrapper;
 mod mem;
 mod microtask;
 mod network_listener;
@@ -132,6 +128,24 @@ mod timers;
 mod unpremultiplytable;
 mod webdriver_handlers;
 
+/// A module with everything layout can use from script.
+///
+/// Try to keep this small!
+///
+/// TODO(emilio): A few of the FooHelpers can go away, presumably...
+pub mod layout_exports {
+    pub use dom::bindings::inheritance::{CharacterDataTypeId, ElementTypeId};
+    pub use dom::bindings::inheritance::{HTMLElementTypeId, NodeTypeId};
+    pub use dom::bindings::js::LayoutJS;
+    pub use dom::characterdata::LayoutCharacterDataHelpers;
+    pub use dom::document::{Document, LayoutDocumentHelpers, PendingRestyle};
+    pub use dom::element::{Element, LayoutElementHelpers, RawLayoutElementHelpers};
+    pub use dom::node::{CAN_BE_FRAGMENTED, DIRTY_ON_VIEWPORT_SIZE_CHANGE, HAS_DIRTY_DESCENDANTS, IS_IN_DOC};
+    pub use dom::node::{HANDLED_SNAPSHOT, HAS_SNAPSHOT};
+    pub use dom::node::{LayoutNodeHelpers, Node};
+    pub use dom::text::Text;
+}
+
 use dom::bindings::codegen::RegisterBindings;
 use dom::bindings::proxyhandler;
 use script_traits::SWManagerSenders;

components/script/test.rs

@@ -24,7 +24,6 @@ pub mod size_of {
     use dom::htmlspanelement::HTMLSpanElement;
     use dom::node::Node;
     use dom::text::Text;
-    use layout_wrapper::{ServoLayoutElement, ServoLayoutNode, ServoThreadSafeLayoutNode};
     use std::mem::size_of;
 
     pub fn CharacterData() -> usize {
@@ -55,18 +54,6 @@ pub mod size_of {
         size_of::<Node>()
     }
 
-    pub fn SendElement() -> usize {
-        size_of::<::style::dom::SendElement<ServoLayoutElement>>()
-    }
-
-    pub fn SendNode() -> usize {
-        size_of::<::style::dom::SendNode<ServoLayoutNode>>()
-    }
-
-    pub fn ServoThreadSafeLayoutNode() -> usize {
-        size_of::<ServoThreadSafeLayoutNode>()
-    }
-
     pub fn Text() -> usize {
         size_of::<Text>()
     }

components/script_layout_interface/wrapper_traits.rs

@@ -87,6 +87,7 @@ pub trait LayoutNode: Debug + GetLayoutData + TNode {
     /// Returns the type ID of this node.
     fn type_id(&self) -> LayoutNodeType;
 
+    unsafe fn initialize_data(&self);
     unsafe fn init_style_and_layout_data(&self, data: OpaqueStyleAndLayoutData);
     unsafe fn take_style_and_layout_data(&self) -> OpaqueStyleAndLayoutData;
 

components/style/dom.rs

@@ -550,6 +550,17 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
     /// traversal. Returns the number of children left to process.
     fn did_process_child(&self) -> isize;
 
+    /// Gets a reference to the ElementData container, or creates one.
+    ///
+    /// Unsafe because it can race to allocate and leak if not used with
+    /// exclusive access to the element.
+    unsafe fn ensure_data(&self) -> AtomicRefMut<ElementData>;
+
+    /// Clears the element data reference, if any.
+    ///
+    /// Unsafe following the same reasoning as ensure_data.
+    unsafe fn clear_data(&self);
+
     /// Gets a reference to the ElementData container.
     fn get_data(&self) -> Option<&AtomicRefCell<ElementData>>;
 

components/style/gecko/traversal.rs

@@ -4,10 +4,8 @@
 
 //! Gecko-specific bits for the styling DOM traversal.
 
-use atomic_refcell::AtomicRefCell;
 use context::{SharedStyleContext, StyleContext};
-use data::ElementData;
+use dom::{NodeInfo, TNode, TElement};
-use dom::{NodeInfo, TNode};
 use gecko::wrapper::{GeckoElement, GeckoNode};
 use traversal::{DomTraversal, PerLevelTraversalData, TraversalDriver, recalc_style_at};
 
@@ -36,7 +34,7 @@ impl<'recalc, 'le> DomTraversal<GeckoElement<'le>> for RecalcStyleOnly<'recalc>
     {
         if node.is_element() {
             let el = node.as_element().unwrap();
-            let mut data = unsafe { el.ensure_data() }.borrow_mut();
+            let mut data = unsafe { el.ensure_data() };
             recalc_style_at(self, traversal_data, context, el, &mut data);
         }
     }
@@ -48,14 +46,6 @@ impl<'recalc, 'le> DomTraversal<GeckoElement<'le>> for RecalcStyleOnly<'recalc>
     /// We don't use the post-order traversal for anything.
     fn needs_postorder_traversal() -> bool { false }
 
-    unsafe fn ensure_element_data<'a>(element: &'a GeckoElement<'le>) -> &'a AtomicRefCell<ElementData> {
-        element.ensure_data()
-    }
-
-    unsafe fn clear_element_data<'a>(element: &'a GeckoElement<'le>) {
-        element.clear_data()
-    }
-
     fn shared_context(&self) -> &SharedStyleContext {
         &self.shared
     }

components/style/gecko/wrapper.rs

@@ -17,7 +17,7 @@
 use CaseSensitivityExt;
 use app_units::Au;
 use applicable_declarations::ApplicableDeclarationBlock;
-use atomic_refcell::AtomicRefCell;
+use atomic_refcell::{AtomicRefCell, AtomicRefMut};
 use context::{QuirksMode, SharedStyleContext, UpdateAnimationsTasks};
 use data::ElementData;
 use dom::{self, DescendantsBit, LayoutIterator, NodeInfo, TElement, TNode, UnsafeNode};
@@ -581,42 +581,6 @@ impl<'le> GeckoElement<'le> {
         self.namespace_id() == (structs::root::kNameSpaceID_XUL as i32)
     }
 
-    /// Clear the element data for a given element.
-    pub fn clear_data(&self) {
-        let ptr = self.0.mServoData.get();
-        unsafe {
-            self.unset_flags(ELEMENT_HAS_SNAPSHOT as u32 |
-                             ELEMENT_HANDLED_SNAPSHOT as u32);
-        }
-        if !ptr.is_null() {
-            debug!("Dropping ElementData for {:?}", self);
-            let data = unsafe { Box::from_raw(self.0.mServoData.get()) };
-            self.0.mServoData.set(ptr::null_mut());
-
-            // Perform a mutable borrow of the data in debug builds. This
-            // serves as an assertion that there are no outstanding borrows
-            // when we destroy the data.
-            debug_assert!({ let _ = data.borrow_mut(); true });
-        }
-    }
-
-    /// Ensures the element has data, returning the existing data or allocating
-    /// it.
-    ///
-    /// Only safe to call with exclusive access to the element, given otherwise
-    /// it could race to allocate and leak.
-    pub unsafe fn ensure_data(&self) -> &AtomicRefCell<ElementData> {
-        match self.get_data() {
-            Some(x) => x,
-            None => {
-                debug!("Creating ElementData for {:?}", self);
-                let ptr = Box::into_raw(Box::new(AtomicRefCell::new(ElementData::default())));
-                self.0.mServoData.set(ptr);
-                unsafe { &* ptr }
-            },
-        }
-    }
-
     /// Sets the specified element data, return any existing data.
     ///
     /// Like `ensure_data`, only safe to call with exclusive access to the
@@ -1067,6 +1031,33 @@ impl<'le> TElement for GeckoElement<'le> {
         unsafe { self.0.mServoData.get().as_ref() }
     }
 
+    unsafe fn ensure_data(&self) -> AtomicRefMut<ElementData> {
+        if self.get_data().is_none() {
+            debug!("Creating ElementData for {:?}", self);
+            let ptr = Box::into_raw(Box::new(AtomicRefCell::new(ElementData::default())));
+            self.0.mServoData.set(ptr);
+        }
+        self.mutate_data().unwrap()
+    }
+
+    unsafe fn clear_data(&self) {
+        let ptr = self.0.mServoData.get();
+        unsafe {
+            self.unset_flags(ELEMENT_HAS_SNAPSHOT as u32 |
+                             ELEMENT_HANDLED_SNAPSHOT as u32);
+        }
+        if !ptr.is_null() {
+            debug!("Dropping ElementData for {:?}", self);
+            let data = unsafe { Box::from_raw(self.0.mServoData.get()) };
+            self.0.mServoData.set(ptr::null_mut());
+
+            // Perform a mutable borrow of the data in debug builds. This
+            // serves as an assertion that there are no outstanding borrows
+            // when we destroy the data.
+            debug_assert!({ let _ = data.borrow_mut(); true });
+        }
+    }
+
     fn skip_root_and_item_based_display_fixup(&self) -> bool {
         // We don't want to fix up display values of native anonymous content.
         // Additionally, we want to skip root-based display fixup for document

components/style/traversal.rs

@@ -4,7 +4,6 @@
 
 //! Traversing the DOM tree; the bloom filter.
 
-use atomic_refcell::AtomicRefCell;
 use context::{ElementCascadeInputs, StyleContext, SharedStyleContext};
 use data::{ElementData, ElementStyles};
 use dom::{NodeInfo, OpaqueNode, TElement, TNode};
@@ -489,20 +488,6 @@ pub trait DomTraversal<E: TElement> : Sync {
         }
     }
 
-    /// Ensures the existence of the ElementData, and returns it. This can't
-    /// live on TNode because of the trait-based separation between Servo's
-    /// script and layout crates.
-    ///
-    /// This is only safe to call in top-down traversal before processing the
-    /// children of |element|.
-    unsafe fn ensure_element_data(element: &E) -> &AtomicRefCell<ElementData>;
-
-    /// Clears the ElementData attached to this element, if any.
-    ///
-    /// This is only safe to call in top-down traversal before processing the
-    /// children of |element|.
-    unsafe fn clear_element_data(element: &E);
-
     /// Return the shared style context common to all worker threads.
     fn shared_context(&self) -> &SharedStyleContext;
 
@@ -647,7 +632,7 @@ where
         if data.styles.is_display_none() {
             debug!("{:?} style is display:none - clearing data from descendants.",
                    element);
-            clear_descendant_data(element, &|e| unsafe { D::clear_element_data(&e) });
+            clear_descendant_data(element)
         }
     }
 
@@ -855,8 +840,7 @@ where
             continue;
         }
 
-        let mut child_data =
+        let mut child_data = unsafe { child.ensure_data() };
-            unsafe { D::ensure_element_data(&child).borrow_mut() };
 
         trace!(" > {:?} -> {:?} + {:?}, pseudo: {:?}",
                child,
@@ -880,13 +864,9 @@ where
 }
 
 /// Clear style data for all the subtree under `el`.
-pub fn clear_descendant_data<E, F>(
+pub fn clear_descendant_data<E>(el: E)
-    el: E,
-    clear_data: &F
-)
 where
     E: TElement,
-    F: Fn(E),
 {
     for kid in el.as_node().traversal_children() {
         if let Some(kid) = kid.as_element() {
@@ -896,8 +876,8 @@ where
             // By consequence, any element without data has no descendants with
             // data.
             if kid.get_data().is_some() {
-                clear_data(kid);
+                unsafe { kid.clear_data() };
-                clear_descendant_data(kid, clear_data);
+                clear_descendant_data(kid);
             }
         }
     }

ports/geckolib/glue.rs

@@ -762,7 +762,7 @@ pub extern "C" fn Servo_StyleWorkerThreadCount() -> u32 {
 
 #[no_mangle]
 pub extern "C" fn Servo_Element_ClearData(element: RawGeckoElementBorrowed) {
-    GeckoElement(element).clear_data();
+    unsafe { GeckoElement(element).clear_data() };
 }
 
 #[no_mangle]
@@ -1531,7 +1531,7 @@ pub extern "C" fn Servo_ResolvePseudoStyle(element: RawGeckoElementBorrowed,
      -> ServoComputedValuesStrong
 {
     let element = GeckoElement(element);
-    let data = unsafe { element.ensure_data() }.borrow_mut();
+    let data = unsafe { element.ensure_data() };
     let doc_data = PerDocumentStyleData::from_ffi(raw_data).borrow();
 
     debug!("Servo_ResolvePseudoStyle: {:?} {:?}, is_probe: {}",
@@ -1582,7 +1582,7 @@ pub extern "C" fn Servo_SetExplicitStyle(element: RawGeckoElementBorrowed,
     // We only support this API for initial styling. There's no reason it couldn't
     // work for other things, we just haven't had a reason to do so.
     debug_assert!(element.get_data().is_none());
-    let mut data = unsafe { element.ensure_data() }.borrow_mut();
+    let mut data = unsafe { element.ensure_data() };
     data.styles.primary = Some(style.clone());
 }
 

tests/unit/script/size_of.rs

@@ -37,8 +37,3 @@ sizeof_checker!(size_div, HTMLDivElement, 392);
 sizeof_checker!(size_span, HTMLSpanElement, 392);
 sizeof_checker!(size_text, Text, 216);
 sizeof_checker!(size_characterdata, CharacterData, 216);
-sizeof_checker!(size_servothreadsafelayoutnode, ServoThreadSafeLayoutNode, 16);
-
-// We use these types in the parallel traversal. They should stay pointer-sized.
-sizeof_checker!(size_sendelement, SendElement, 8);
-sizeof_checker!(size_sendnode, SendNode, 8);