chore: Clean up use of gfx and constellation types (#31981)

This change contains three semi-related clean ups:

1. the `to_webrender()` and `from_webrender()` functions on Pipeline are
   turned into more-idiomatic `From` and `Into` implementations.
2. `combine_id_with_fragment_type` now returns a `u64` as that is what is
   expected for all callers and not a `usize`.
3. The `query_scroll_id` query is removed entirely. The
   `ExternalScrollId` that this queries is easily generated directly
   from the node's opaque id. Querying into layout isn't necessary at
   all.

components/compositing/compositor.rs

@@ -8,7 +8,6 @@ use std::env;
 use std::fs::{create_dir_all, File};
 use std::io::Write;
 use std::iter::once;
-use std::num::NonZeroU32;
 use std::rc::Rc;
 use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 
@@ -27,9 +26,7 @@ use image::{DynamicImage, ImageFormat};
 use ipc_channel::ipc;
 use libc::c_void;
 use log::{debug, error, info, trace, warn};
-use msg::constellation_msg::{
+use msg::constellation_msg::{PipelineId, TopLevelBrowsingContextId, WebViewId};
-    PipelineId, PipelineIndex, PipelineNamespaceId, TopLevelBrowsingContextId, WebViewId,
-};
 use net_traits::image::base::Image;
 use net_traits::image_cache::CorsStatus;
 use pixels::PixelFormat;
@@ -79,20 +76,6 @@ enum NotReadyToPaint {
 const MAX_ZOOM: f32 = 8.0;
 const MIN_ZOOM: f32 = 0.1;
 
-trait ConvertPipelineIdFromWebRender {
-    #[allow(clippy::wrong_self_convention)]
-    fn from_webrender(&self) -> PipelineId;
-}
-
-impl ConvertPipelineIdFromWebRender for WebRenderPipelineId {
-    fn from_webrender(&self) -> PipelineId {
-        PipelineId {
-            namespace_id: PipelineNamespaceId(self.0),
-            index: PipelineIndex(NonZeroU32::new(self.1).expect("Webrender pipeline zero?")),
-        }
-    }
-}
-
 /// Holds the state when running reftests that determines when it is
 /// safe to save the output image.
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -725,7 +708,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                     external_scroll_id,
                 ),
             ) => {
-                let pipeline_id = PipelineId::from_webrender(pipeline_id);
+                let pipeline_id = pipeline_id.into();
                 let pipeline_details = match self.pipeline_details.get_mut(&pipeline_id) {
                     Some(details) => details,
                     None => return,
@@ -798,7 +781,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                 );
 
                 let pipeline_id = display_list_info.pipeline_id;
-                let details = self.pipeline_details(PipelineId::from_webrender(pipeline_id));
+                let details = self.pipeline_details(pipeline_id.into());
                 details.most_recent_display_list_epoch = Some(display_list_info.epoch);
                 details.hit_test_items = display_list_info.hit_test_info;
                 details.install_new_scroll_tree(display_list_info.scroll_tree);
@@ -1114,7 +1097,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                         spatial_id: zoom_reference_frame,
                         clip_chain_id,
                     },
-                    pipeline_id.to_webrender(),
+                    pipeline_id.into(),
                     true,
                 );
             }
@@ -1480,7 +1463,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
             .items
             .iter()
             .filter_map(|item| {
-                let pipeline_id = PipelineId::from_webrender(item.pipeline);
+                let pipeline_id = item.pipeline.into();
                 let details = match self.pipeline_details.get(&pipeline_id) {
                     Some(details) => details,
                     None => return None,
@@ -1949,10 +1932,9 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                 // frame tree.
                 let mut pipeline_epochs = HashMap::new();
                 for id in self.pipeline_details.keys() {
-                    let webrender_pipeline_id = id.to_webrender();
                     if let Some(WebRenderEpoch(epoch)) = self
                         .webrender
-                        .current_epoch(self.webrender_document, webrender_pipeline_id)
+                        .current_epoch(self.webrender_document, id.into())
                     {
                         let epoch = Epoch(epoch);
                         pipeline_epochs.insert(*id, epoch);
@@ -2104,7 +2086,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                 // we get the last painted frame id from webrender
                 if let Some(WebRenderEpoch(epoch)) = self
                     .webrender
-                    .current_epoch(self.webrender_document, id.to_webrender())
+                    .current_epoch(self.webrender_document, id.into())
                 {
                     // and check if it is the one layout is expecting,
                     let epoch = Epoch(epoch);

components/layout/display_list/builder.rs

@@ -2270,7 +2270,7 @@ impl Fragment {
     fn unique_id(&self) -> u64 {
         let fragment_type = self.fragment_type();
         let id = self.node.id();
-        combine_id_with_fragment_type(id, fragment_type) as u64
+        combine_id_with_fragment_type(id, fragment_type)
     }
 
     fn fragment_type(&self) -> FragmentType {
@@ -2737,8 +2737,7 @@ impl BlockFlow {
         let content_size = self.base.overflow.scroll.origin + self.base.overflow.scroll.size;
         let content_size = Size2D::new(content_size.x, content_size.y);
 
-        let external_id =
+        let external_id = ExternalScrollId(self.fragment.unique_id(), state.pipeline_id.into());
-            ExternalScrollId(self.fragment.unique_id(), state.pipeline_id.to_webrender());
         let new_clip_scroll_index = state.add_clip_scroll_node(ClipScrollNode {
             parent_index: self.clipping_and_scrolling().scrolling,
             clip,

components/layout/display_list/webrender_helpers.rs

@@ -133,7 +133,7 @@ impl DisplayList {
         viewport_size: LayoutSize,
         epoch: Epoch,
     ) -> (DisplayListBuilder, CompositorDisplayListInfo, IsContentful) {
-        let webrender_pipeline = pipeline_id.to_webrender();
+        let webrender_pipeline = pipeline_id.into();
         let mut builder = DisplayListBuilder::new(webrender_pipeline);
         builder.begin();
 
@@ -314,7 +314,7 @@ impl DisplayItem {
                         spatial_id: common.spatial_id,
                         clip_chain_id: common.clip_chain_id,
                     },
-                    item.iframe.to_webrender(),
+                    item.iframe.into(),
                     true,
                 );
                 IsContentful(false)

components/layout/query.rs

@@ -9,7 +9,6 @@ use std::ops::Deref;
 
 use app_units::Au;
 use euclid::default::{Box2D, Point2D, Rect, Size2D, Vector2D};
-use msg::constellation_msg::PipelineId;
 use script_layout_interface::wrapper_traits::{
     LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode,
 };
@@ -31,7 +30,6 @@ use style::selector_parser::PseudoElement;
 use style::shared_lock::SharedRwLock;
 use style::stylesheets::{CssRuleType, Origin, UrlExtraData};
 use style_traits::{ParsingMode, ToCss};
-use webrender_api::ExternalScrollId;
 
 use crate::construct::ConstructionResult;
 use crate::display_list::items::OpaqueNode;
@@ -571,14 +569,6 @@ pub fn process_client_rect_query(
     iterator.client_rect
 }
 
-pub fn process_node_scroll_id_request<'dom>(
-    id: PipelineId,
-    requested_node: impl LayoutNode<'dom>,
-) -> ExternalScrollId {
-    let layout_node = requested_node.to_threadsafe();
-    layout_node.generate_scroll_id(id)
-}
-
 /// <https://drafts.csswg.org/cssom-view/#scrolling-area>
 pub fn process_scrolling_area_request(
     requested_node: Option<OpaqueNode>,

components/layout_2020/display_list/mod.rs

@@ -291,7 +291,7 @@ impl Fragment {
                             spatial_id: common.spatial_id,
                             clip_chain_id: common.clip_chain_id,
                         },
-                        iframe.pipeline_id.to_webrender(),
+                        iframe.pipeline_id.into(),
                         true,
                     );
                 },

components/layout_2020/fragment_tree/base_fragment.rs

@@ -126,6 +126,6 @@ impl Tag {
             Some(PseudoElement::After) => FragmentType::AfterPseudoContent,
             _ => FragmentType::FragmentBody,
         };
-        combine_id_with_fragment_type(self.node.id(), fragment_type) as u64
+        combine_id_with_fragment_type(self.node.id(), fragment_type)
     }
 }

components/layout_2020/query.rs

@@ -9,7 +9,6 @@ use app_units::Au;
 use euclid::default::{Point2D, Rect};
 use euclid::{SideOffsets2D, Size2D, Vector2D};
 use log::warn;
-use msg::constellation_msg::PipelineId;
 use script_layout_interface::wrapper_traits::{
     LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode,
 };
@@ -31,7 +30,6 @@ use style::stylist::RuleInclusion;
 use style::traversal::resolve_style;
 use style::values::generics::font::LineHeight;
 use style_traits::{ParsingMode, ToCss};
-use webrender_api::ExternalScrollId;
 
 use crate::fragment_tree::{Fragment, FragmentFlags, FragmentTree, Tag};
 
@@ -71,14 +69,6 @@ pub fn process_node_geometry_request(
     }
 }
 
-pub fn process_node_scroll_id_request<'dom>(
-    id: PipelineId,
-    requested_node: impl LayoutNode<'dom>,
-) -> ExternalScrollId {
-    let layout_node = requested_node.to_threadsafe();
-    layout_node.generate_scroll_id(id)
-}
-
 /// <https://drafts.csswg.org/cssom-view/#scrolling-area>
 pub fn process_node_scroll_area_request(
     requested_node: Option<OpaqueNode>,

components/layout_thread/lib.rs

@@ -39,7 +39,7 @@ use layout::flow_ref::FlowRef;
 use layout::incremental::{RelayoutMode, SpecialRestyleDamage};
 use layout::query::{
     process_client_rect_query, process_content_box_request, process_content_boxes_request,
-    process_element_inner_text_query, process_node_scroll_id_request, process_offset_parent_query,
+    process_element_inner_text_query, process_offset_parent_query,
     process_resolved_font_style_request, process_resolved_style_request,
     process_scrolling_area_request,
 };
@@ -365,9 +365,9 @@ impl Layout for LayoutThread {
         flags.insert(HitTestFlags::POINT_RELATIVE_TO_PIPELINE_VIEWPORT);
 
         let client_point = units::DevicePoint::from_untyped(point);
-        let results =
+        let results = self
-            self.webrender_api
+            .webrender_api
-                .hit_test(Some(self.id.to_webrender()), client_point, flags);
+            .hit_test(Some(self.id.into()), client_point, flags);
 
         results.iter().map(|result| result.node).collect()
     }
@@ -451,14 +451,6 @@ impl Layout for LayoutThread {
         )
     }
 
-    fn query_scroll_id(
-        &self,
-        node: script_layout_interface::TrustedNodeAddress,
-    ) -> webrender_api::ExternalScrollId {
-        let node = unsafe { ServoLayoutNode::new(&node) };
-        process_node_scroll_id_request(self.id, node)
-    }
-
     fn query_scrolling_area(&self, node: Option<OpaqueNode>) -> UntypedRect<i32> {
         let Some(mut root_flow) = self.root_flow_for_query() else {
             return UntypedRect::zero();
@@ -504,7 +496,7 @@ impl LayoutThread {
         window_size: WindowSizeData,
     ) -> LayoutThread {
         // Let webrender know about this pipeline by sending an empty display list.
-        webrender_api.send_initial_transaction(id.to_webrender());
+        webrender_api.send_initial_transaction(id.into());
 
         let device = Device::new(
             MediaType::screen(),
@@ -1238,7 +1230,7 @@ impl LayoutThread {
 
         let point = Point2D::new(-state.scroll_offset.x, -state.scroll_offset.y);
         self.webrender_api.send_scroll_node(
-            self.id.to_webrender(),
+            self.id.into(),
             units::LayoutPoint::from_untyped(point),
             state.scroll_id,
         );

components/layout_thread_2020/lib.rs

@@ -30,9 +30,8 @@ use layout::context::LayoutContext;
 use layout::display_list::{DisplayList, WebRenderImageInfo};
 use layout::query::{
     process_content_box_request, process_content_boxes_request, process_element_inner_text_query,
-    process_node_geometry_request, process_node_scroll_area_request,
+    process_node_geometry_request, process_node_scroll_area_request, process_offset_parent_query,
-    process_node_scroll_id_request, process_offset_parent_query, process_resolved_font_style_query,
+    process_resolved_font_style_query, process_resolved_style_request, process_text_index_request,
-    process_resolved_style_request, process_text_index_request,
 };
 use layout::traversal::RecalcStyle;
 use layout::{layout_debug, BoxTree, FragmentTree};
@@ -328,9 +327,9 @@ impl Layout for LayoutThread {
         flags.insert(HitTestFlags::POINT_RELATIVE_TO_PIPELINE_VIEWPORT);
 
         let client_point = units::DevicePoint::from_untyped(point);
-        let results =
+        let results = self
-            self.webrender_api
+            .webrender_api
-                .hit_test(Some(self.id.to_webrender()), client_point, flags);
+            .hit_test(Some(self.id.into()), client_point, flags);
 
         results.iter().map(|result| result.node).collect()
     }
@@ -406,14 +405,6 @@ impl Layout for LayoutThread {
         )
     }
 
-    fn query_scroll_id(
-        &self,
-        node: script_layout_interface::TrustedNodeAddress,
-    ) -> ExternalScrollId {
-        let node = unsafe { ServoLayoutNode::new(&node) };
-        process_node_scroll_id_request(self.id, node)
-    }
-
     fn query_scrolling_area(&self, node: Option<OpaqueNode>) -> UntypedRect<i32> {
         process_node_scroll_area_request(node, self.fragment_tree.borrow().clone())
     }
@@ -452,7 +443,7 @@ impl LayoutThread {
         window_size: WindowSizeData,
     ) -> LayoutThread {
         // Let webrender know about this pipeline by sending an empty display list.
-        webrender_api_sender.send_initial_transaction(id.to_webrender());
+        webrender_api_sender.send_initial_transaction(id.into());
 
         // The device pixel ratio is incorrect (it does not have the hidpi value),
         // but it will be set correctly when the initial reflow takes place.
@@ -878,7 +869,7 @@ impl LayoutThread {
             .insert(state.scroll_id, state.scroll_offset);
         let point = Point2D::new(-state.scroll_offset.x, -state.scroll_offset.y);
         self.webrender_api.send_scroll_node(
-            self.id.to_webrender(),
+            self.id.into(),
             units::LayoutPoint::from_untyped(point),
             state.scroll_id,
         );
@@ -950,7 +941,7 @@ impl LayoutThread {
         let mut display_list = DisplayList::new(
             viewport_size,
             fragment_tree.scrollable_overflow(),
-            self.id.to_webrender(),
+            self.id.into(),
             epoch.into(),
             fragment_tree.root_scroll_sensitivity,
         );

components/script/dom/window.rs

@@ -26,6 +26,7 @@ use dom_struct::dom_struct;
 use embedder_traits::{EmbedderMsg, PromptDefinition, PromptOrigin, PromptResult};
 use euclid::default::{Point2D as UntypedPoint2D, Rect as UntypedRect};
 use euclid::{Point2D, Rect, Scale, Size2D, Vector2D};
+use gfx_traits::combine_id_with_fragment_type;
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use js::conversions::ToJSValConvertible;
@@ -2101,20 +2102,19 @@ impl Window {
 
     // https://drafts.csswg.org/cssom-view/#element-scrolling-members
     pub fn scroll_node(&self, node: &Node, x_: f64, y_: f64, behavior: ScrollBehavior) {
-        if !self.layout_reflow(QueryMsg::NodeScrollIdQuery) {
-            return;
-        }
-
         // The scroll offsets are immediatly updated since later calls
         // to topScroll and others may access the properties before
         // webrender has a chance to update the offsets.
         self.scroll_offsets
             .borrow_mut()
             .insert(node.to_opaque(), Vector2D::new(x_ as f32, y_ as f32));
-
+        let scroll_id = ExternalScrollId(
-        let scroll_id = self
+            combine_id_with_fragment_type(
-            .with_layout(|layout| layout.query_scroll_id(node.to_trusted_node_address()))
+                node.to_opaque().id(),
-            .unwrap();
+                gfx_traits::FragmentType::FragmentBody,
+            ),
+            self.pipeline_id().into(),
+        );
 
         // Step 12
         self.perform_a_scroll(
@@ -2720,7 +2720,6 @@ fn debug_reflow_events(id: PipelineId, reflow_goal: &ReflowGoal, reason: &Reflow
             QueryMsg::NodesFromPointQuery => "\tNodesFromPointQuery",
             QueryMsg::ClientRectQuery => "\tClientRectQuery",
             QueryMsg::ScrollingAreaQuery => "\tNodeScrollGeometryQuery",
-            QueryMsg::NodeScrollIdQuery => "\tNodeScrollIdQuery",
             QueryMsg::ResolvedStyleQuery => "\tResolvedStyleQuery",
             QueryMsg::ResolvedFontStyleQuery => "\nResolvedFontStyleQuery",
             QueryMsg::OffsetParentQuery => "\tOffsetParentQuery",

components/shared/gfx/lib.rs

@@ -8,7 +8,7 @@
 
 pub mod print_tree;
 
-use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicU64, Ordering};
 
 use malloc_size_of_derive::MallocSizeOf;
 use range::{int_range_index, RangeIndex};
@@ -90,30 +90,30 @@ pub enum FragmentType {
 /// The next ID that will be used for a special scroll root id.
 ///
 /// A special scroll root is a scroll root that is created for generated content.
-static NEXT_SPECIAL_SCROLL_ROOT_ID: AtomicUsize = AtomicUsize::new(0);
+static NEXT_SPECIAL_SCROLL_ROOT_ID: AtomicU64 = AtomicU64::new(0);
 
 /// If none of the bits outside this mask are set, the scroll root is a special scroll root.
 /// Note that we assume that the top 16 bits of the address space are unused on the platform.
-const SPECIAL_SCROLL_ROOT_ID_MASK: usize = 0xffff;
+const SPECIAL_SCROLL_ROOT_ID_MASK: u64 = 0xffff;
 
 /// Returns a new scroll root ID for a scroll root.
-fn next_special_id() -> usize {
+fn next_special_id() -> u64 {
     // We shift this left by 2 to make room for the fragment type ID.
     ((NEXT_SPECIAL_SCROLL_ROOT_ID.fetch_add(1, Ordering::SeqCst) + 1) << 2) &
         SPECIAL_SCROLL_ROOT_ID_MASK
 }
 
-pub fn combine_id_with_fragment_type(id: usize, fragment_type: FragmentType) -> usize {
+pub fn combine_id_with_fragment_type(id: usize, fragment_type: FragmentType) -> u64 {
     debug_assert_eq!(id & (fragment_type as usize), 0);
     if fragment_type == FragmentType::FragmentBody {
-        id
+        id as u64
     } else {
-        next_special_id() | (fragment_type as usize)
+        next_special_id() | (fragment_type as u64)
     }
 }
 
 pub fn node_id_from_scroll_id(id: usize) -> Option<usize> {
-    if (id & !SPECIAL_SCROLL_ROOT_ID_MASK) != 0 {
+    if (id as u64 & !SPECIAL_SCROLL_ROOT_ID_MASK) != 0 {
         return Some(id & !3);
     }
     None

components/shared/msg/constellation_msg.rs

@@ -223,14 +223,14 @@ impl PipelineId {
         })
     }
 
-    pub fn to_webrender(&self) -> WebRenderPipelineId {
+    pub fn root_scroll_id(&self) -> webrender_api::ExternalScrollId {
-        let PipelineNamespaceId(namespace_id) = self.namespace_id;
+        ExternalScrollId(0, self.into())
-        let PipelineIndex(index) = self.index;
-        WebRenderPipelineId(namespace_id, index.get())
     }
+}
 
+impl From<WebRenderPipelineId> for PipelineId {
     #[allow(unsafe_code)]
-    pub fn from_webrender(pipeline: WebRenderPipelineId) -> PipelineId {
+    fn from(pipeline: WebRenderPipelineId) -> Self {
         let WebRenderPipelineId(namespace_id, index) = pipeline;
         unsafe {
             PipelineId {
@@ -239,9 +239,19 @@ impl PipelineId {
             }
         }
     }
+}
 
-    pub fn root_scroll_id(&self) -> webrender_api::ExternalScrollId {
+impl From<PipelineId> for WebRenderPipelineId {
-        ExternalScrollId(0, self.to_webrender())
+    fn from(value: PipelineId) -> Self {
+        let PipelineNamespaceId(namespace_id) = value.namespace_id;
+        let PipelineIndex(index) = value.index;
+        WebRenderPipelineId(namespace_id, index.get())
+    }
+}
+
+impl From<&PipelineId> for WebRenderPipelineId {
+    fn from(value: &PipelineId) -> Self {
+        (*value).into()
     }
 }
 

components/shared/script_layout/lib.rs

@@ -46,7 +46,7 @@ use style::properties::PropertyId;
 use style::selector_parser::PseudoElement;
 use style::stylesheets::Stylesheet;
 use style_traits::CSSPixel;
-use webrender_api::{ExternalScrollId, ImageKey};
+use webrender_api::ImageKey;
 
 pub type GenericLayoutData = dyn Any + Send + Sync;
 
@@ -235,7 +235,6 @@ pub trait Layout {
         animations: DocumentAnimationSet,
         animation_timeline_value: f64,
     ) -> Option<ServoArc<Font>>;
-    fn query_scroll_id(&self, node: TrustedNodeAddress) -> ExternalScrollId;
     fn query_scrolling_area(&self, node: Option<OpaqueNode>) -> Rect<i32>;
     fn query_text_indext(&self, node: OpaqueNode, point: Point2D<f32>) -> Option<usize>;
 }

components/shared/script_layout/message.rs

@@ -55,7 +55,6 @@ pub enum QueryMsg {
     OffsetParentQuery,
     TextIndexQuery,
     NodesFromPointQuery,
-    NodeScrollIdQuery,
     ResolvedStyleQuery,
     StyleQuery,
     ElementInnerTextQuery,
@@ -90,7 +89,6 @@ impl ReflowGoal {
                 QueryMsg::ClientRectQuery |
                 QueryMsg::ContentBox |
                 QueryMsg::ContentBoxes |
-                QueryMsg::NodeScrollIdQuery |
                 QueryMsg::OffsetParentQuery |
                 QueryMsg::ResolvedFontStyleQuery |
                 QueryMsg::ScrollingAreaQuery |
@@ -112,7 +110,6 @@ impl ReflowGoal {
                 QueryMsg::ContentBoxes |
                 QueryMsg::ClientRectQuery |
                 QueryMsg::ScrollingAreaQuery |
-                QueryMsg::NodeScrollIdQuery |
                 QueryMsg::ResolvedStyleQuery |
                 QueryMsg::ResolvedFontStyleQuery |
                 QueryMsg::OffsetParentQuery |

components/shared/script_layout/wrapper_traits.rs

@@ -9,7 +9,7 @@ use std::fmt::Debug;
 use std::sync::Arc as StdArc;
 
 use atomic_refcell::AtomicRef;
-use gfx_traits::{combine_id_with_fragment_type, ByteIndex, FragmentType};
+use gfx_traits::{ByteIndex, FragmentType};
 use html5ever::{local_name, namespace_url, ns, LocalName, Namespace};
 use msg::constellation_msg::{BrowsingContextId, PipelineId};
 use net_traits::image::base::{Image, ImageMetadata};
@@ -23,7 +23,6 @@ use style::dom::{LayoutIterator, NodeInfo, OpaqueNode, TElement, TNode};
 use style::properties::ComputedValues;
 use style::selector_parser::{PseudoElement, PseudoElementCascadeType, SelectorImpl};
 use style::stylist::RuleInclusion;
-use webrender_api::ExternalScrollId;
 
 use crate::{
     GenericLayoutData, HTMLCanvasData, HTMLMediaData, LayoutNodeType, SVGSVGData, StyleData,
@@ -315,11 +314,6 @@ pub trait ThreadSafeLayoutNode<'dom>: Clone + Copy + Debug + NodeInfo + PartialE
     fn fragment_type(&self) -> FragmentType {
         self.get_pseudo_element_type().fragment_type()
     }
-
-    fn generate_scroll_id(&self, pipeline_id: PipelineId) -> ExternalScrollId {
-        let id = combine_id_with_fragment_type(self.opaque().id(), self.fragment_type());
-        ExternalScrollId(id as u64, pipeline_id.to_webrender())
-    }
 }
 
 pub trait ThreadSafeLayoutElement<'dom>: