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diff --git a/gfx/wr/webrender/src/prim_store/gradient/conic.rs b/gfx/wr/webrender/src/prim_store/gradient/conic.rs
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+++ b/gfx/wr/webrender/src/prim_store/gradient/conic.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Conic gradients
+//!
+//! Specification: https://drafts.csswg.org/css-images-4/#conic-gradients
+//!
+//! Conic gradients are rendered via cached render tasks and composited with the image brush.
+
+use euclid::vec2;
+use api::{ExtendMode, GradientStop, PremultipliedColorF};
+use api::units::*;
+use crate::scene_building::IsVisible;
+use crate::frame_builder::FrameBuildingState;
+use crate::intern::{Internable, InternDebug, Handle as InternHandle};
+use crate::internal_types::LayoutPrimitiveInfo;
+use crate::prim_store::{BrushSegment, GradientTileRange};
+use crate::prim_store::{PrimitiveInstanceKind, PrimitiveOpacity, FloatKey};
+use crate::prim_store::{PrimKeyCommonData, PrimTemplateCommonData, PrimitiveStore};
+use crate::prim_store::{NinePatchDescriptor, PointKey, SizeKey, InternablePrimitive};
+use crate::render_task::{RenderTask, RenderTaskKind};
+use crate::render_task_graph::RenderTaskId;
+use crate::render_task_cache::{RenderTaskCacheKeyKind, RenderTaskCacheKey, RenderTaskParent};
+use crate::renderer::GpuBufferAddress;
+use crate::picture::{SurfaceIndex};
+
+use std::{hash, ops::{Deref, DerefMut}};
+use super::{stops_and_min_alpha, GradientStopKey, GradientGpuBlockBuilder};
+
+/// Hashable conic gradient parameters, for use during prim interning.
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(Debug, Clone, MallocSizeOf, PartialEq)]
+pub struct ConicGradientParams {
+    pub angle: f32, // in radians
+    pub start_offset: f32,
+    pub end_offset: f32,
+}
+
+impl Eq for ConicGradientParams {}
+
+impl hash::Hash for ConicGradientParams {
+    fn hash<H: hash::Hasher>(&self, state: &mut H) {
+        self.angle.to_bits().hash(state);
+        self.start_offset.to_bits().hash(state);
+        self.end_offset.to_bits().hash(state);
+    }
+}
+
+/// Identifying key for a line decoration.
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(Debug, Clone, Eq, PartialEq, Hash, MallocSizeOf)]
+pub struct ConicGradientKey {
+    pub common: PrimKeyCommonData,
+    pub extend_mode: ExtendMode,
+    pub center: PointKey,
+    pub params: ConicGradientParams,
+    pub stretch_size: SizeKey,
+    pub stops: Vec<GradientStopKey>,
+    pub tile_spacing: SizeKey,
+    pub nine_patch: Option<Box<NinePatchDescriptor>>,
+}
+
+impl ConicGradientKey {
+    pub fn new(
+        info: &LayoutPrimitiveInfo,
+        conic_grad: ConicGradient,
+    ) -> Self {
+        ConicGradientKey {
+            common: info.into(),
+            extend_mode: conic_grad.extend_mode,
+            center: conic_grad.center,
+            params: conic_grad.params,
+            stretch_size: conic_grad.stretch_size,
+            stops: conic_grad.stops,
+            tile_spacing: conic_grad.tile_spacing,
+            nine_patch: conic_grad.nine_patch,
+        }
+    }
+}
+
+impl InternDebug for ConicGradientKey {}
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+pub struct ConicGradientTemplate {
+    pub common: PrimTemplateCommonData,
+    pub extend_mode: ExtendMode,
+    pub center: DevicePoint,
+    pub params: ConicGradientParams,
+    pub task_size: DeviceIntSize,
+    pub scale: DeviceVector2D,
+    pub stretch_size: LayoutSize,
+    pub tile_spacing: LayoutSize,
+    pub brush_segments: Vec<BrushSegment>,
+    pub stops_opacity: PrimitiveOpacity,
+    pub stops: Vec<GradientStop>,
+    pub src_color: Option<RenderTaskId>,
+}
+
+impl Deref for ConicGradientTemplate {
+    type Target = PrimTemplateCommonData;
+    fn deref(&self) -> &Self::Target {
+        &self.common
+    }
+}
+
+impl DerefMut for ConicGradientTemplate {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.common
+    }
+}
+
+impl From<ConicGradientKey> for ConicGradientTemplate {
+    fn from(item: ConicGradientKey) -> Self {
+        let common = PrimTemplateCommonData::with_key_common(item.common);
+        let mut brush_segments = Vec::new();
+
+        if let Some(ref nine_patch) = item.nine_patch {
+            brush_segments = nine_patch.create_segments(common.prim_rect.size());
+        }
+
+        let (stops, min_alpha) = stops_and_min_alpha(&item.stops);
+
+        // Save opacity of the stops for use in
+        // selecting which pass this gradient
+        // should be drawn in.
+        let stops_opacity = PrimitiveOpacity::from_alpha(min_alpha);
+
+        let mut stretch_size: LayoutSize = item.stretch_size.into();
+        stretch_size.width = stretch_size.width.min(common.prim_rect.width());
+        stretch_size.height = stretch_size.height.min(common.prim_rect.height());
+
+        fn approx_eq(a: f32, b: f32) -> bool { (a - b).abs() < 0.01 }
+
+        // Attempt to detect some of the common configurations with hard gradient stops. Allow
+        // those a higher maximum resolution to avoid the worst cases of aliasing artifacts with
+        // large conic gradients. A better solution would be to go back to rendering very large
+        // conic gradients via a brush shader instead of caching all of them (unclear whether
+        // it is important enough to warrant the better solution).
+        let mut has_hard_stops = false;
+        let mut prev_stop = None;
+        let offset_range = item.params.end_offset - item.params.start_offset;
+        for stop in &stops {
+            if offset_range <= 0.0 {
+                break;
+            }
+            if let Some(prev_offset) = prev_stop {
+                // Check whether two consecutive stops are very close (hard stops).
+                if stop.offset < prev_offset + 0.005 / offset_range {
+                    // a is the angle of the stop normalized into 0-1 space and repeating in the 0-0.25 range.
+                    // If close to 0.0 or 0.25 it means the stop is vertical or horizontal. For those, the lower
+                    // resolution isn't a big issue.
+                    let a = item.params.angle / (2.0 * std::f32::consts::PI)
+                        + item.params.start_offset
+                        + stop.offset / offset_range;
+                    let a = a.rem_euclid(0.25);
+
+                    if !approx_eq(a, 0.0) && !approx_eq(a, 0.25) {
+                        has_hard_stops = true;
+                        break;
+                    }
+                }
+            }
+            prev_stop = Some(stop.offset);
+        }
+
+        let max_size = if has_hard_stops {
+            2048.0
+        } else {
+            1024.0
+        };
+
+        // Avoid rendering enormous gradients. Radial gradients are mostly made of soft transitions,
+        // so it is unlikely that rendering at a higher resolution that 1024 would produce noticeable
+        // differences, especially with 8 bits per channel.
+        let mut task_size: DeviceSize = stretch_size.cast_unit();
+        let mut scale = vec2(1.0, 1.0);
+        if task_size.width > max_size {
+            scale.x = task_size.width / max_size;
+            task_size.width = max_size;
+        }
+        if task_size.height > max_size {
+            scale.y = task_size.height / max_size;
+            task_size.height = max_size;
+        }
+
+        ConicGradientTemplate {
+            common,
+            center: DevicePoint::new(item.center.x, item.center.y),
+            extend_mode: item.extend_mode,
+            params: item.params,
+            stretch_size,
+            task_size: task_size.ceil().to_i32(),
+            scale,
+            tile_spacing: item.tile_spacing.into(),
+            brush_segments,
+            stops_opacity,
+            stops,
+            src_color: None,
+        }
+    }
+}
+
+impl ConicGradientTemplate {
+    /// Update the GPU cache for a given primitive template. This may be called multiple
+    /// times per frame, by each primitive reference that refers to this interned
+    /// template. The initial request call to the GPU cache ensures that work is only
+    /// done if the cache entry is invalid (due to first use or eviction).
+    pub fn update(
+        &mut self,
+        frame_state: &mut FrameBuildingState,
+        parent_surface: SurfaceIndex,
+    ) {
+        if let Some(mut request) =
+            frame_state.gpu_cache.request(&mut self.common.gpu_cache_handle) {
+            // write_prim_gpu_blocks
+            request.push(PremultipliedColorF::WHITE);
+            request.push(PremultipliedColorF::WHITE);
+            request.push([
+                self.stretch_size.width,
+                self.stretch_size.height,
+                0.0,
+                0.0,
+            ]);
+
+            // write_segment_gpu_blocks
+            for segment in &self.brush_segments {
+                // has to match VECS_PER_SEGMENT
+                request.write_segment(
+                    segment.local_rect,
+                    segment.extra_data,
+                );
+            }
+        }
+
+        let cache_key = ConicGradientCacheKey {
+            size: self.task_size,
+            center: PointKey { x: self.center.x, y: self.center.y },
+            scale: PointKey { x: self.scale.x, y: self.scale.y },
+            start_offset: FloatKey(self.params.start_offset),
+            end_offset: FloatKey(self.params.end_offset),
+            angle: FloatKey(self.params.angle),
+            extend_mode: self.extend_mode,
+            stops: self.stops.iter().map(|stop| (*stop).into()).collect(),
+        };
+
+        let task_id = frame_state.resource_cache.request_render_task(
+            RenderTaskCacheKey {
+                size: self.task_size,
+                kind: RenderTaskCacheKeyKind::ConicGradient(cache_key),
+            },
+            frame_state.gpu_cache,
+            frame_state.frame_gpu_data,
+            frame_state.rg_builder,
+            None,
+            false,
+            RenderTaskParent::Surface(parent_surface),
+            &mut frame_state.surface_builder,
+            |rg_builder, gpu_buffer_builder| {
+                let stops = GradientGpuBlockBuilder::build(
+                    false,
+                    gpu_buffer_builder,
+                    &self.stops,
+                );
+
+                rg_builder.add().init(RenderTask::new_dynamic(
+                    self.task_size,
+                    RenderTaskKind::ConicGradient(ConicGradientTask {
+                        extend_mode: self.extend_mode,
+                        scale: self.scale,
+                        center: self.center,
+                        params: self.params.clone(),
+                        stops,
+                    }),
+                ))
+            }
+        );
+
+        self.src_color = Some(task_id);
+
+        // Tile spacing is always handled by decomposing into separate draw calls so the
+        // primitive opacity is equivalent to stops opacity. This might change to being
+        // set to non-opaque in the presence of tile spacing if/when tile spacing is handled
+        // in the same way as with the image primitive.
+        self.opacity = self.stops_opacity;
+    }
+}
+
+pub type ConicGradientDataHandle = InternHandle<ConicGradient>;
+
+#[derive(Debug, MallocSizeOf)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct ConicGradient {
+    pub extend_mode: ExtendMode,
+    pub center: PointKey,
+    pub params: ConicGradientParams,
+    pub stretch_size: SizeKey,
+    pub stops: Vec<GradientStopKey>,
+    pub tile_spacing: SizeKey,
+    pub nine_patch: Option<Box<NinePatchDescriptor>>,
+}
+
+impl Internable for ConicGradient {
+    type Key = ConicGradientKey;
+    type StoreData = ConicGradientTemplate;
+    type InternData = ();
+    const PROFILE_COUNTER: usize = crate::profiler::INTERNED_CONIC_GRADIENTS;
+}
+
+impl InternablePrimitive for ConicGradient {
+    fn into_key(
+        self,
+        info: &LayoutPrimitiveInfo,
+    ) -> ConicGradientKey {
+        ConicGradientKey::new(info, self)
+    }
+
+    fn make_instance_kind(
+        _key: ConicGradientKey,
+        data_handle: ConicGradientDataHandle,
+        _prim_store: &mut PrimitiveStore,
+        _reference_frame_relative_offset: LayoutVector2D,
+    ) -> PrimitiveInstanceKind {
+        PrimitiveInstanceKind::ConicGradient {
+            data_handle,
+            visible_tiles_range: GradientTileRange::empty(),
+        }
+    }
+}
+
+impl IsVisible for ConicGradient {
+    fn is_visible(&self) -> bool {
+        true
+    }
+}
+
+#[derive(Debug)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct ConicGradientTask {
+    pub extend_mode: ExtendMode,
+    pub center: DevicePoint,
+    pub scale: DeviceVector2D,
+    pub params: ConicGradientParams,
+    pub stops: GpuBufferAddress,
+}
+
+impl ConicGradientTask {
+    pub fn to_instance(&self, target_rect: &DeviceIntRect) -> ConicGradientInstance {
+        ConicGradientInstance {
+            task_rect: target_rect.to_f32(),
+            center: self.center,
+            scale: self.scale,
+            start_offset: self.params.start_offset,
+            end_offset: self.params.end_offset,
+            angle: self.params.angle,
+            extend_mode: self.extend_mode as i32,
+            gradient_stops_address: self.stops.as_int(),
+        }
+    }
+}
+
+/// The per-instance shader input of a radial gradient render task.
+///
+/// Must match the RADIAL_GRADIENT instance description in renderer/vertex.rs.
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[repr(C)]
+#[derive(Clone, Debug)]
+pub struct ConicGradientInstance {
+    pub task_rect: DeviceRect,
+    pub center: DevicePoint,
+    pub scale: DeviceVector2D,
+    pub start_offset: f32,
+    pub end_offset: f32,
+    pub angle: f32,
+    pub extend_mode: i32,
+    pub gradient_stops_address: i32,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct ConicGradientCacheKey {
+    pub size: DeviceIntSize,
+    pub center: PointKey,
+    pub scale: PointKey,
+    pub start_offset: FloatKey,
+    pub end_offset: FloatKey,
+    pub angle: FloatKey,
+    pub extend_mode: ExtendMode,
+    pub stops: Vec<GradientStopKey>,
+}
+