Auto merge of #23017 - emilio:gecko-sync, r=emilio

style: Sync changes from mozilla-central.

See each individual commit for details.

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74 files changed, 1144 insertions, 1525 deletions

diff --git a/components/layout/display_list/builder.rs b/components/layout/display_list/builder.rs
index d26cd6b9c32..73343c3a4f2 100644
--- a/components/layout/display_list/builder.rs
+++ b/components/layout/display_list/builder.rs
@@ -58,7 +58,7 @@ use style::properties::{style_structs, ComputedValues};
 use style::servo::restyle_damage::ServoRestyleDamage;
 use style::values::computed::effects::SimpleShadow;
 use style::values::computed::image::Image as ComputedImage;
-use style::values::computed::Gradient;
+use style::values::computed::{Gradient, LengthOrAuto};
 use style::values::generics::background::BackgroundSize;
 use style::values::generics::image::{GradientKind, Image, PaintWorklet};
 use style::values::specified::ui::CursorKind;
@@ -2627,19 +2627,22 @@ impl BlockFlow {
             _ => return,
         }
 
+        fn extract_clip_component(p: &LengthOrAuto) -> Option<Au> {
+            match *p {
+                LengthOrAuto::Auto => None,
+                LengthOrAuto::LengthPercentage(ref length) => Some(Au::from(*length)),
+            }
+        }
+
         let clip_origin = Point2D::new(
             stacking_relative_border_box.origin.x +
-                style_clip_rect.left.map(Au::from).unwrap_or(Au(0)),
+                extract_clip_component(&style_clip_rect.left).unwrap_or_default(),
             stacking_relative_border_box.origin.y +
-                style_clip_rect.top.map(Au::from).unwrap_or(Au(0)),
+                extract_clip_component(&style_clip_rect.top).unwrap_or_default(),
         );
-        let right = style_clip_rect
-            .right
-            .map(Au::from)
+        let right = extract_clip_component(&style_clip_rect.right)
             .unwrap_or(stacking_relative_border_box.size.width);
-        let bottom = style_clip_rect
-            .bottom
-            .map(Au::from)
+        let bottom = extract_clip_component(&style_clip_rect.bottom)
             .unwrap_or(stacking_relative_border_box.size.height);
         let clip_size = Size2D::new(right - clip_origin.x, bottom - clip_origin.y);
 
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index d8183eae1c9..ff62cc79638 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -64,6 +64,7 @@ use style::values::computed::counters::ContentItem;
 use style::values::computed::{LengthPercentage, LengthPercentageOrAuto, Size};
 use style::values::generics::box_::{Perspective, VerticalAlign};
 use style::values::generics::transform;
+use style::Zero;
 use webrender_api::{self, LayoutTransform};
 
 // From gfxFontConstants.h in Firefox.
diff --git a/components/layout/multicol.rs b/components/layout/multicol.rs
index ca92c200d40..f8ddfa8200c 100644
--- a/components/layout/multicol.rs
+++ b/components/layout/multicol.rs
@@ -19,7 +19,7 @@ use std::fmt;
 use std::sync::Arc;
 use style::logical_geometry::LogicalSize;
 use style::properties::ComputedValues;
-use style::values::computed::{MaxSize, Size};
+use style::values::computed::length::{MaxSize, NonNegativeLengthOrAuto, Size};
 use style::values::generics::column::ColumnCount;
 use style::values::Either;
 
@@ -114,7 +114,9 @@ impl Flow for MulticolFlow {
 
             let column_style = style.get_column();
             let mut column_count;
-            if let Either::First(column_width) = column_style.column_width {
+            if let NonNegativeLengthOrAuto::LengthPercentage(column_width) =
+                column_style.column_width
+            {
                 let column_width = Au::from(column_width);
                 column_count = max(
                     1,
diff --git a/components/layout/text.rs b/components/layout/text.rs
index aba5703a1c6..b26e531e670 100644
--- a/components/layout/text.rs
+++ b/components/layout/text.rs
@@ -14,7 +14,6 @@ use gfx::font::{FontMetrics, FontRef, RunMetrics, ShapingFlags, ShapingOptions};
 use gfx::text::glyph::ByteIndex;
 use gfx::text::text_run::TextRun;
 use gfx::text::util::{self, CompressionMode};
-use ordered_float::NotNan;
 use range::Range;
 use servo_atoms::Atom;
 use std::borrow::ToOwned;
@@ -196,11 +195,7 @@ impl TextRunScanner {
                 };
                 text_transform = inherited_text_style.text_transform;
                 letter_spacing = inherited_text_style.letter_spacing;
-                word_spacing = inherited_text_style
-                    .word_spacing
-                    .value()
-                    .map(|lop| lop.to_hash_key())
-                    .unwrap_or((Au(0), NotNan::new(0.0).unwrap()));
+                word_spacing = inherited_text_style.word_spacing.to_hash_key();
                 text_rendering = inherited_text_style.text_rendering;
                 word_break = inherited_text_style.word_break;
             }
@@ -321,10 +316,8 @@ impl TextRunScanner {
             // example, `finally` with a wide `letter-spacing` renders as `f i n a l l y` and not
             // `fi n a l l y`.
             let mut flags = ShapingFlags::empty();
-            if let Some(v) = letter_spacing.value() {
-                if v.px() != 0. {
-                    flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG);
-                }
+            if letter_spacing.0.px() != 0. {
+                flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG);
             }
             if text_rendering == TextRendering::Optimizespeed {
                 flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG);
@@ -334,8 +327,12 @@ impl TextRunScanner {
                 flags.insert(ShapingFlags::KEEP_ALL_FLAG);
             }
             let options = ShapingOptions {
-                letter_spacing: letter_spacing.value().cloned().map(Au::from),
-                word_spacing: word_spacing,
+                letter_spacing: if letter_spacing.0.px() == 0. {
+                    None
+                } else {
+                    Some(Au::from(letter_spacing.0))
+                },
+                word_spacing,
                 script: Script::Common,
                 flags: flags,
             };
diff --git a/components/style/cbindgen.toml b/components/style/cbindgen.toml
index 0b8719c4dbf..5de390cc8a6 100644
--- a/components/style/cbindgen.toml
+++ b/components/style/cbindgen.toml
@@ -13,6 +13,7 @@ autogen_warning = """/* DO NOT MODIFY THIS MANUALLY! This file was generated usi
 class nsAtom;
 namespace mozilla {
   class WritingMode;
+  enum HalfCorner : uint8_t;
   enum LogicalSide : uint8_t;
   namespace css {
     struct URLValue;
@@ -39,8 +40,13 @@ include = ["cssparser", "style_traits"]
 derive_eq = true
 derive_neq = true
 
+[macro_expansion]
+bitflags = true
+
 [enum]
 derive_helper_methods = true
+derive_const_casts = true
+cast_assert_name = "MOZ_ASSERT"
 
 [export]
 prefix = "Style"
@@ -77,8 +83,10 @@ include = [
   "Resize",
   "Overflow",
   "LengthPercentage",
+  "LetterSpacing",
   "NonNegativeLengthPercentage",
   "LengthPercentageOrAuto",
+  "LineHeight",
   "NonNegativeLengthPercentageOrAuto",
   "Rect",
   "IntersectionObserverRootMargin",
@@ -88,16 +96,20 @@ include = [
   "Position",
   "BackgroundSize",
   "BorderImageSlice",
+  "BorderSpacing",
+  "BorderRadius",
   "NonNegativeLengthOrNumberRect",
   "Perspective",
   "ZIndex",
   "TransformOrigin",
+  "WordBreak",
 ]
 item_types = ["enums", "structs", "typedefs"]
 
 [export.body]
 "CSSPixelLength" = """
   inline nscoord ToAppUnits() const;
+  inline bool IsZero() const;
 """
 
 "LengthPercentage" = """
@@ -114,6 +126,7 @@ item_types = ["enums", "structs", "typedefs"]
   inline bool ConvertsToPercentage() const;
   inline bool HasLengthAndPercentage() const;
   inline float ToPercentage() const;
+  inline bool IsDefinitelyZero() const;
   inline CSSCoord ResolveToCSSPixels(CSSCoord aPercentageBasisInCSSPixels) const;
   template<typename T> inline CSSCoord ResolveToCSSPixelsWith(T aPercentageGetter) const;
   template<typename T, typename U>
@@ -125,7 +138,6 @@ item_types = ["enums", "structs", "typedefs"]
 """
 
 "GenericLengthPercentageOrAuto" = """
-  inline const StyleLengthPercentage& AsLengthPercentage() const;
   inline bool ConvertsToLength() const;
   inline nscoord ToLength() const;
   inline bool ConvertsToPercentage() const;
@@ -135,8 +147,6 @@ item_types = ["enums", "structs", "typedefs"]
 """
 
 "GenericSize" = """
-  inline const StyleLengthPercentage& AsLengthPercentage() const;
-  inline StyleExtremumLength AsExtremumLength() const;
   inline bool ConvertsToLength() const;
   inline nscoord ToLength() const;
   inline bool ConvertsToPercentage() const;
@@ -148,12 +158,9 @@ item_types = ["enums", "structs", "typedefs"]
 
 "GenericFlexBasis" = """
   inline bool IsAuto() const;
-  inline const StyleSize& AsSize() const;
 """
 
 "GenericMaxSize" = """
-  inline const StyleLengthPercentage& AsLengthPercentage() const;
-  inline StyleExtremumLength AsExtremumLength() const;
   inline bool ConvertsToLength() const;
   inline nscoord ToLength() const;
   inline bool ConvertsToPercentage() const;
@@ -185,3 +192,7 @@ item_types = ["enums", "structs", "typedefs"]
   inline const T& GetIEnd(mozilla::WritingMode) const;
   inline const T& GetBEnd(mozilla::WritingMode) const;
 """
+
+"GenericBorderRadius" = """
+  inline const StyleLengthPercentage& Get(mozilla::HalfCorner) const;
+"""
diff --git a/components/style/custom_properties.rs b/components/style/custom_properties.rs
index f21929c7079..0dbd611820d 100644
--- a/components/style/custom_properties.rs
+++ b/components/style/custom_properties.rs
@@ -7,8 +7,9 @@
 //! [custom]: https://drafts.csswg.org/css-variables/
 
 use crate::hash::map::Entry;
-use crate::properties::{CSSWideKeyword, CustomDeclarationValue};
+use crate::properties::{CSSWideKeyword, CustomDeclaration, CustomDeclarationValue};
 use crate::selector_map::{PrecomputedHashMap, PrecomputedHashSet, PrecomputedHasher};
+use crate::stylesheets::{Origin, PerOrigin};
 use crate::Atom;
 use cssparser::{Delimiter, Parser, ParserInput, SourcePosition, Token, TokenSerializationType};
 use indexmap::IndexMap;
@@ -490,6 +491,7 @@ fn parse_env_function<'i, 't>(
 /// properties.
 pub struct CustomPropertiesBuilder<'a> {
     seen: PrecomputedHashSet<&'a Name>,
+    reverted: PerOrigin<PrecomputedHashSet<&'a Name>>,
     may_have_cycles: bool,
     custom_properties: Option<CustomPropertiesMap>,
     inherited: Option<&'a Arc<CustomPropertiesMap>>,
@@ -504,6 +506,7 @@ impl<'a> CustomPropertiesBuilder<'a> {
     ) -> Self {
         Self {
             seen: PrecomputedHashSet::default(),
+            reverted: Default::default(),
             may_have_cycles: false,
             custom_properties: None,
             inherited,
@@ -512,13 +515,22 @@ impl<'a> CustomPropertiesBuilder<'a> {
     }
 
     /// Cascade a given custom property declaration.
-    pub fn cascade(&mut self, name: &'a Name, specified_value: &CustomDeclarationValue) {
+    pub fn cascade(&mut self, declaration: &'a CustomDeclaration, origin: Origin) {
+        let CustomDeclaration {
+            ref name,
+            ref value,
+        } = *declaration;
+
+        if self.reverted.borrow_for_origin(&origin).contains(&name) {
+            return;
+        }
+
         let was_already_present = !self.seen.insert(name);
         if was_already_present {
             return;
         }
 
-        if !self.value_may_affect_style(name, specified_value) {
+        if !self.value_may_affect_style(name, value) {
             return;
         }
 
@@ -530,7 +542,7 @@ impl<'a> CustomPropertiesBuilder<'a> {
         }
 
         let map = self.custom_properties.as_mut().unwrap();
-        match *specified_value {
+        match *value {
             CustomDeclarationValue::Value(ref unparsed_value) => {
                 let has_references = !unparsed_value.references.is_empty();
                 self.may_have_cycles |= has_references;
@@ -554,6 +566,12 @@ impl<'a> CustomPropertiesBuilder<'a> {
                 map.insert(name.clone(), value);
             },
             CustomDeclarationValue::CSSWideKeyword(keyword) => match keyword {
+                CSSWideKeyword::Revert => {
+                    self.seen.remove(name);
+                    for origin in origin.following_including() {
+                        self.reverted.borrow_mut_for_origin(&origin).insert(name);
+                    }
+                },
                 CSSWideKeyword::Initial => {
                     map.remove(name);
                 },
@@ -587,10 +605,10 @@ impl<'a> CustomPropertiesBuilder<'a> {
                 // not existing in the map.
                 return false;
             },
-            (Some(existing_value), &CustomDeclarationValue::Value(ref specified_value)) => {
+            (Some(existing_value), &CustomDeclarationValue::Value(ref value)) => {
                 // Don't bother overwriting an existing inherited value with
                 // the same specified value.
-                if existing_value == specified_value {
+                if existing_value == value {
                     return false;
                 }
             },
diff --git a/components/style/gecko/conversions.rs b/components/style/gecko/conversions.rs
index 2a2ae268395..64f0726b21e 100644
--- a/components/style/gecko/conversions.rs
+++ b/components/style/gecko/conversions.rs
@@ -27,6 +27,7 @@ use crate::values::generics::box_::VerticalAlign;
 use crate::values::generics::grid::{TrackListValue, TrackSize};
 use crate::values::generics::image::{CompatMode, GradientItem, Image as GenericImage};
 use crate::values::generics::rect::Rect;
+use crate::Zero;
 use app_units::Au;
 use std::f32::consts::PI;
 use style_traits::values::specified::AllowedNumericType;
@@ -575,17 +576,15 @@ pub mod basic_shape {
     //! Conversions from and to CSS shape representations.
 
     use crate::gecko::values::GeckoStyleCoordConvertible;
-    use crate::gecko_bindings::structs::{nsStyleCoord, nsStyleCorners};
+    use crate::gecko_bindings::structs::nsStyleCoord;
     use crate::gecko_bindings::structs::{StyleBasicShape, StyleBasicShapeType};
     use crate::gecko_bindings::structs::{
         StyleGeometryBox, StyleShapeSource, StyleShapeSourceType,
     };
-    use crate::gecko_bindings::sugar::ns_style_coord::{CoordDataMut, CoordDataValue};
     use crate::gecko_bindings::sugar::refptr::RefPtr;
     use crate::values::computed::basic_shape::{
         BasicShape, ClippingShape, FloatAreaShape, ShapeRadius,
     };
-    use crate::values::computed::border::{BorderCornerRadius, BorderRadius};
     use crate::values::computed::length::LengthPercentage;
     use crate::values::computed::motion::OffsetPath;
     use crate::values::computed::url::ComputedUrl;
@@ -594,9 +593,7 @@ pub mod basic_shape {
     };
     use crate::values::generics::basic_shape::{Circle, Ellipse, Path, PolygonCoord};
     use crate::values::generics::basic_shape::{GeometryBox, ShapeBox, ShapeSource};
-    use crate::values::generics::border::BorderRadius as GenericBorderRadius;
     use crate::values::generics::rect::Rect;
-    use crate::values::generics::NonNegative;
     use crate::values::specified::SVGPathData;
     use std::borrow::Borrow;
 
@@ -706,8 +703,7 @@ pub mod basic_shape {
                     let r = LengthPercentage::from_gecko_style_coord(&other.mCoordinates[1]);
                     let b = LengthPercentage::from_gecko_style_coord(&other.mCoordinates[2]);
                     let l = LengthPercentage::from_gecko_style_coord(&other.mCoordinates[3]);
-                    let round: BorderRadius = (&other.mRadius).into();
-                    let round = if round.all_zero() { None } else { Some(round) };
+                    let round = other.mRadius;
                     let rect = Rect::new(
                         t.expect("inset() offset should be a length, percentage, or calc value"),
                         r.expect("inset() offset should be a length, percentage, or calc value"),
@@ -752,65 +748,6 @@ pub mod basic_shape {
         }
     }
 
-    impl<'a> From<&'a nsStyleCorners> for BorderRadius {
-        fn from(other: &'a nsStyleCorners) -> Self {
-            let get_corner = |index| {
-                BorderCornerRadius::new(
-                    NonNegative(
-                        LengthPercentage::from_gecko_style_coord(&other.data_at(index)).expect(
-                            "<border-radius> should be a length, percentage, or calc value",
-                        ),
-                    ),
-                    NonNegative(
-                        LengthPercentage::from_gecko_style_coord(&other.data_at(index + 1)).expect(
-                            "<border-radius> should be a length, percentage, or calc value",
-                        ),
-                    ),
-                )
-            };
-
-            GenericBorderRadius {
-                top_left: get_corner(0),
-                top_right: get_corner(2),
-                bottom_right: get_corner(4),
-                bottom_left: get_corner(6),
-            }
-        }
-    }
-
-    // Can't be a From impl since we need to set an existing
-    // nsStyleCorners, not create a new one
-    impl BorderRadius {
-        /// Set this `BorderRadius` into a given `nsStyleCoord`.
-        pub fn set_corners(&self, other: &mut nsStyleCorners) {
-            let mut set_corner = |field: &BorderCornerRadius, index| {
-                field
-                    .0
-                    .width()
-                    .to_gecko_style_coord(&mut other.data_at_mut(index));
-                field
-                    .0
-                    .height()
-                    .to_gecko_style_coord(&mut other.data_at_mut(index + 1));
-            };
-            set_corner(&self.top_left, 0);
-            set_corner(&self.top_right, 2);
-            set_corner(&self.bottom_right, 4);
-            set_corner(&self.bottom_left, 6);
-        }
-    }
-
-    /// We use None for a nonexistant radius, but Gecko uses (0 0 0 0 / 0 0 0 0)
-    pub fn set_corners_from_radius(radius: Option<BorderRadius>, other: &mut nsStyleCorners) {
-        if let Some(radius) = radius {
-            radius.set_corners(other);
-        } else {
-            for i in 0..8 {
-                other.data_at_mut(i).set_value(CoordDataValue::Coord(0));
-            }
-        }
-    }
-
     impl<'a> From<&'a nsStyleCoord> for ShapeRadius {
         fn from(other: &'a nsStyleCoord) -> Self {
             let other = other.borrow();
diff --git a/components/style/gecko/data.rs b/components/style/gecko/data.rs
index 80e34fe2e7e..b70f376d7e6 100644
--- a/components/style/gecko/data.rs
+++ b/components/style/gecko/data.rs
@@ -7,7 +7,7 @@
 use crate::context::QuirksMode;
 use crate::dom::TElement;
 use crate::gecko_bindings::bindings::{self, RawServoStyleSet};
-use crate::gecko_bindings::structs::{RawGeckoPresContextBorrowed, ServoStyleSetSizes};
+use crate::gecko_bindings::structs::{self, ServoStyleSetSizes};
 use crate::gecko_bindings::structs::{StyleSheet as DomStyleSheet, StyleSheetInfo};
 use crate::gecko_bindings::sugar::ownership::{HasArcFFI, HasBoxFFI, HasFFI, HasSimpleFFI};
 use crate::invalidation::media_queries::{MediaListKey, ToMediaListKey};
@@ -142,15 +142,15 @@ pub struct PerDocumentStyleDataImpl {
 pub struct PerDocumentStyleData(AtomicRefCell<PerDocumentStyleDataImpl>);
 
 impl PerDocumentStyleData {
-    /// Create a dummy `PerDocumentStyleData`.
-    pub fn new(pres_context: RawGeckoPresContextBorrowed) -> Self {
-        let device = Device::new(pres_context);
+    /// Create a `PerDocumentStyleData`.
+    pub fn new(document: *const structs::Document) -> Self {
+        let device = Device::new(document);
 
         // FIXME(emilio, tlin): How is this supposed to work with XBL? This is
         // right now not always honored, see bug 1405543...
         //
         // Should we just force XBL Stylists to be NoQuirks?
-        let quirks_mode = unsafe { (*device.pres_context().mDocument.mRawPtr).mCompatMode };
+        let quirks_mode = device.document().mCompatMode;
 
         PerDocumentStyleData(AtomicRefCell::new(PerDocumentStyleDataImpl {
             stylist: Stylist::new(device, quirks_mode.into()),
@@ -191,8 +191,7 @@ impl PerDocumentStyleDataImpl {
     /// Returns whether visited styles are enabled.
     #[inline]
     pub fn visited_styles_enabled(&self) -> bool {
-        let doc = self.stylist.device().pres_context().mDocument.mRawPtr;
-        unsafe { bindings::Gecko_VisitedStylesEnabled(doc) }
+        unsafe { bindings::Gecko_VisitedStylesEnabled(self.stylist.device().document()) }
     }
 
     /// Measure heap usage.
diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index 2547f2a45d4..9c48836b4d9 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -17,12 +17,13 @@ use app_units::Au;
 use euclid::Size2D;
 
 fn viewport_size(device: &Device) -> Size2D<Au> {
-    let pc = device.pres_context();
-    if pc.mIsRootPaginatedDocument() != 0 {
-        // We want the page size, including unprintable areas and margins.
-        // FIXME(emilio, bug 1414600): Not quite!
-        let area = &pc.mPageSize;
-        return Size2D::new(Au(area.width), Au(area.height));
+    if let Some(pc) = device.pres_context() {
+        if pc.mIsRootPaginatedDocument() != 0 {
+            // We want the page size, including unprintable areas and margins.
+            // FIXME(emilio, bug 1414600): Not quite!
+            let area = &pc.mPageSize;
+            return Size2D::new(Au(area.width), Au(area.height));
+        }
     }
     device.au_viewport_size()
 }
diff --git a/components/style/gecko/media_queries.rs b/components/style/gecko/media_queries.rs
index 8fa2258eaaf..4c04d9573e5 100644
--- a/components/style/gecko/media_queries.rs
+++ b/components/style/gecko/media_queries.rs
@@ -8,7 +8,6 @@ use crate::custom_properties::CssEnvironment;
 use crate::gecko::values::{convert_nscolor_to_rgba, convert_rgba_to_nscolor};
 use crate::gecko_bindings::bindings;
 use crate::gecko_bindings::structs;
-use crate::gecko_bindings::structs::{nsPresContext, RawGeckoPresContextBorrowed};
 use crate::media_queries::MediaType;
 use crate::properties::ComputedValues;
 use crate::string_cache::Atom;
@@ -28,10 +27,9 @@ use style_traits::{CSSPixel, DevicePixel};
 /// The `Device` in Gecko wraps a pres context, has a default values computed,
 /// and contains all the viewport rule state.
 pub struct Device {
-    /// NB: The pres context lifetime is tied to the styleset, who owns the
-    /// stylist, and thus the `Device`, so having a raw pres context pointer
-    /// here is fine.
-    pres_context: RawGeckoPresContextBorrowed,
+    /// NB: The document owns the styleset, who owns the stylist, and thus the
+    /// `Device`, so having a raw document pointer here is fine.
+    document: *const structs::Document,
     default_values: Arc<ComputedValues>,
     /// The font size of the root element
     /// This is set when computing the style of the root
@@ -81,16 +79,16 @@ unsafe impl Send for Device {}
 
 impl Device {
     /// Trivially constructs a new `Device`.
-    pub fn new(pres_context: RawGeckoPresContextBorrowed) -> Self {
-        assert!(!pres_context.is_null());
+    pub fn new(document: *const structs::Document) -> Self {
+        assert!(!document.is_null());
+        let doc = unsafe { &*document };
+        let prefs = unsafe { &*bindings::Gecko_GetPrefSheetPrefs(doc) };
         Device {
-            pres_context,
-            default_values: ComputedValues::default_values(unsafe {
-                &*(*pres_context).mDocument.mRawPtr
-            }),
+            document,
+            default_values: ComputedValues::default_values(doc),
             // FIXME(bz): Seems dubious?
             root_font_size: AtomicIsize::new(FontSize::medium().size().0 as isize),
-            body_text_color: AtomicUsize::new(unsafe { &*pres_context }.mDefaultColor as usize),
+            body_text_color: AtomicUsize::new(prefs.mDefaultColor as usize),
             used_root_font_size: AtomicBool::new(false),
             used_viewport_size: AtomicBool::new(false),
             environment: CssEnvironment,
@@ -112,11 +110,13 @@ impl Device {
     /// Whether any animation name may be referenced from the style of any
     /// element.
     pub fn animation_name_may_be_referenced(&self, name: &KeyframesName) -> bool {
+        let pc = match self.pres_context() {
+            Some(pc) => pc,
+            None => return false,
+        };
+
         unsafe {
-            bindings::Gecko_AnimationNameMayBeReferencedFromStyle(
-                self.pres_context(),
-                name.as_atom().as_ptr(),
-            )
+            bindings::Gecko_AnimationNameMayBeReferencedFromStyle(pc, name.as_atom().as_ptr())
         }
     }
 
@@ -156,16 +156,29 @@ impl Device {
         convert_nscolor_to_rgba(self.body_text_color.load(Ordering::Relaxed) as u32)
     }
 
+    /// Gets the document pointer.
+    #[inline]
+    pub fn document(&self) -> &structs::Document {
+        unsafe { &*self.document }
+    }
+
     /// Gets the pres context associated with this document.
     #[inline]
-    pub fn pres_context(&self) -> &nsPresContext {
-        unsafe { &*self.pres_context }
+    pub fn pres_context(&self) -> Option<&structs::nsPresContext> {
+        unsafe {
+            self.document()
+                .mPresShell
+                .as_ref()?
+                .mPresContext
+                .mRawPtr
+                .as_ref()
+        }
     }
 
-    /// Gets the document pointer.
+    /// Gets the preference stylesheet prefs for our document.
     #[inline]
-    pub fn document(&self) -> &structs::Document {
-        unsafe { &*self.pres_context().mDocument.mRawPtr }
+    pub fn pref_sheet_prefs(&self) -> &structs::PreferenceSheet_Prefs {
+        unsafe { &*bindings::Gecko_GetPrefSheetPrefs(self.document()) }
     }
 
     /// Recreates the default computed values.
@@ -195,13 +208,17 @@ impl Device {
 
     /// Returns the current media type of the device.
     pub fn media_type(&self) -> MediaType {
+        let pc = match self.pres_context() {
+            Some(pc) => pc,
+            None => return MediaType::screen(),
+        };
+
         // Gecko allows emulating random media with mIsEmulatingMedia and
         // mMediaEmulated.
-        let context = self.pres_context();
-        let medium_to_use = if context.mIsEmulatingMedia() != 0 {
-            context.mMediaEmulated.mRawPtr
+        let medium_to_use = if pc.mIsEmulatingMedia() != 0 {
+            pc.mMediaEmulated.mRawPtr
         } else {
-            context.mMedium
+            pc.mMedium
         };
 
         MediaType(CustomIdent(unsafe { Atom::from_raw(medium_to_use) }))
@@ -209,7 +226,11 @@ impl Device {
 
     /// Returns the current viewport size in app units.
     pub fn au_viewport_size(&self) -> Size2D<Au> {
-        let area = &self.pres_context().mVisibleArea;
+        let pc = match self.pres_context() {
+            Some(pc) => pc,
+            None => return Size2D::new(Au(0), Au(0)),
+        };
+        let area = &pc.mVisibleArea;
         Size2D::new(Au(area.width), Au(area.height))
     }
 
@@ -227,34 +248,62 @@ impl Device {
 
     /// Returns the device pixel ratio.
     pub fn device_pixel_ratio(&self) -> TypedScale<f32, CSSPixel, DevicePixel> {
-        let override_dppx = self.pres_context().mOverrideDPPX;
+        let pc = match self.pres_context() {
+            Some(pc) => pc,
+            None => return TypedScale::new(1.),
+        };
+
+        let override_dppx = pc.mOverrideDPPX;
         if override_dppx > 0.0 {
             return TypedScale::new(override_dppx);
         }
-        let au_per_dpx = self.pres_context().mCurAppUnitsPerDevPixel as f32;
+
+        let au_per_dpx = pc.mCurAppUnitsPerDevPixel as f32;
         let au_per_px = AU_PER_PX as f32;
         TypedScale::new(au_per_px / au_per_dpx)
     }
 
     /// Returns whether document colors are enabled.
+    #[inline]
     pub fn use_document_colors(&self) -> bool {
-        self.pres_context().mUseDocumentColors() != 0
+        let doc = self.document();
+        if doc.mIsBeingUsedAsImage() {
+            return true;
+        }
+        let document_color_use =
+            unsafe { structs::StaticPrefs_sVarCache_browser_display_document_color_use };
+        let prefs = self.pref_sheet_prefs();
+        match document_color_use {
+            1 => true,
+            2 => prefs.mIsChrome,
+            _ => !prefs.mUseAccessibilityTheme,
+        }
     }
 
     /// Returns the default background color.
     pub fn default_background_color(&self) -> RGBA {
-        convert_nscolor_to_rgba(self.pres_context().mBackgroundColor)
+        convert_nscolor_to_rgba(self.pref_sheet_prefs().mDefaultBackgroundColor)
+    }
+
+    /// Returns the current effective text zoom.
+    #[inline]
+    fn effective_text_zoom(&self) -> f32 {
+        let pc = match self.pres_context() {
+            Some(pc) => pc,
+            None => return 1.,
+        };
+        pc.mEffectiveTextZoom
     }
 
     /// Applies text zoom to a font-size or line-height value (see nsStyleFont::ZoomText).
     #[inline]
     pub fn zoom_text(&self, size: Au) -> Au {
-        size.scale_by(self.pres_context().mEffectiveTextZoom)
+        size.scale_by(self.effective_text_zoom())
     }
 
     /// Un-apply text zoom.
     #[inline]
     pub fn unzoom_text(&self, size: Au) -> Au {
-        size.scale_by(1. / self.pres_context().mEffectiveTextZoom)
+        size.scale_by(1. / self.effective_text_zoom())
     }
 }
diff --git a/components/style/gecko/values.rs b/components/style/gecko/values.rs
index fa1c7d1f6d3..6b3e7a676e0 100644
--- a/components/style/gecko/values.rs
+++ b/components/style/gecko/values.rs
@@ -19,7 +19,7 @@ use crate::values::generics::grid::{TrackBreadth, TrackKeyword};
 use crate::values::generics::length::LengthPercentageOrAuto;
 use crate::values::generics::{CounterStyleOrNone, NonNegative};
 use crate::values::{Auto, Either, None_, Normal};
-use crate::Atom;
+use crate::{Atom, Zero};
 use app_units::Au;
 use cssparser::RGBA;
 use nsstring::{nsACString, nsCStr};
diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index 97f0f887a00..f5058fc63c4 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -1044,9 +1044,13 @@ impl FontMetricsProvider for GeckoFontMetricsProvider {
         device: &Device,
     ) -> FontMetricsQueryResult {
         use crate::gecko_bindings::bindings::Gecko_GetFontMetrics;
+        let pc = match device.pres_context() {
+            Some(pc) => pc,
+            None => return FontMetricsQueryResult::NotAvailable,
+        };
         let gecko_metrics = unsafe {
             Gecko_GetFontMetrics(
-                device.pres_context(),
+                pc,
                 wm.is_vertical() && !wm.is_sideways(),
                 font.gecko(),
                 font_size.0,
@@ -1242,8 +1246,7 @@ impl<'le> TElement for GeckoElement<'le> {
     }
 
     fn owner_doc_matches_for_testing(&self, device: &Device) -> bool {
-        self.as_node().owner_doc().0 as *const structs::Document ==
-            device.pres_context().mDocument.mRawPtr
+        self.as_node().owner_doc().0 as *const structs::Document == device.document() as *const _
     }
 
     fn style_attribute(&self) -> Option<ArcBorrow<Locked<PropertyDeclarationBlock>>> {
diff --git a/components/style/gecko_bindings/sugar/ns_css_value.rs b/components/style/gecko_bindings/sugar/ns_css_value.rs
index ef971c669ad..b59732bcc8e 100644
--- a/components/style/gecko_bindings/sugar/ns_css_value.rs
+++ b/components/style/gecko_bindings/sugar/ns_css_value.rs
@@ -10,6 +10,7 @@ use crate::gecko_bindings::structs::{nsCSSUnit, nsCSSValue};
 use crate::gecko_bindings::structs::{nsCSSValueList, nsCSSValue_Array};
 use crate::gecko_string_cache::Atom;
 use crate::values::computed::{Angle, Length, LengthPercentage, Percentage};
+use crate::Zero;
 use std::marker::PhantomData;
 use std::mem;
 use std::ops::{Index, IndexMut};
diff --git a/components/style/gecko_bindings/sugar/ns_style_coord.rs b/components/style/gecko_bindings/sugar/ns_style_coord.rs
index 4f188297d5e..7c6612f35ef 100644
--- a/components/style/gecko_bindings/sugar/ns_style_coord.rs
+++ b/components/style/gecko_bindings/sugar/ns_style_coord.rs
@@ -5,8 +5,8 @@
 //! Rust helpers for Gecko's `nsStyleCoord`.
 
 use crate::gecko_bindings::bindings;
+use crate::gecko_bindings::structs::nsStyleSides;
 use crate::gecko_bindings::structs::{nsStyleCoord, nsStyleCoord_Calc, nsStyleCoord_CalcValue};
-use crate::gecko_bindings::structs::{nsStyleCorners, nsStyleSides};
 use crate::gecko_bindings::structs::{nsStyleUnion, nsStyleUnit, nscoord};
 use std::mem;
 
@@ -123,64 +123,6 @@ unsafe impl<'a> CoordDataMut for SidesDataMut<'a> {
     }
 }
 
-impl nsStyleCorners {
-    /// Get a `nsStyleCoord` like object representing the given index's value
-    /// and unit.
-    #[inline]
-    pub fn data_at(&self, index: usize) -> CornersData {
-        CornersData {
-            corners: self,
-            index: index,
-        }
-    }
-
-    /// Get a `nsStyleCoord` like object representing the mutable given index's
-    /// value and unit.
-    #[inline]
-    pub fn data_at_mut(&mut self, index: usize) -> CornersDataMut {
-        CornersDataMut {
-            corners: self,
-            index: index,
-        }
-    }
-}
-
-/// A `nsStyleCoord`-like struct on top of `nsStyleCorners`.
-pub struct CornersData<'a> {
-    corners: &'a nsStyleCorners,
-    index: usize,
-}
-
-/// A `nsStyleCoord`-like struct on top of a mutable `nsStyleCorners` reference.
-pub struct CornersDataMut<'a> {
-    corners: &'a mut nsStyleCorners,
-    index: usize,
-}
-
-unsafe impl<'a> CoordData for CornersData<'a> {
-    fn unit(&self) -> nsStyleUnit {
-        unsafe { self.corners.get_mUnits()[self.index] }
-    }
-    fn union(&self) -> nsStyleUnion {
-        unsafe { self.corners.get_mValues()[self.index] }
-    }
-}
-unsafe impl<'a> CoordData for CornersDataMut<'a> {
-    fn unit(&self) -> nsStyleUnit {
-        unsafe { self.corners.get_mUnits()[self.index] }
-    }
-    fn union(&self) -> nsStyleUnion {
-        unsafe { self.corners.get_mValues()[self.index] }
-    }
-}
-unsafe impl<'a> CoordDataMut for CornersDataMut<'a> {
-    unsafe fn values_mut(&mut self) -> (&mut nsStyleUnit, &mut nsStyleUnion) {
-        let unit = &mut self.corners.get_mUnits_mut()[self.index] as *mut _;
-        let value = &mut self.corners.get_mValues_mut()[self.index] as *mut _;
-        (&mut *unit, &mut *value)
-    }
-}
-
 /// Enum representing the tagged union that is CoordData.
 ///
 /// In release mode this should never actually exist in the code, and will be
diff --git a/components/style/lib.rs b/components/style/lib.rs
index 2ea20088ed0..37b464afb47 100644
--- a/components/style/lib.rs
+++ b/components/style/lib.rs
@@ -244,3 +244,26 @@ impl CaseSensitivityExt for selectors::attr::CaseSensitivity {
         }
     }
 }
+
+/// A trait pretty much similar to num_traits::Zero, but without the need of
+/// implementing `Add`.
+pub trait Zero {
+    /// Returns the zero value.
+    fn zero() -> Self;
+
+    /// Returns whether this value is zero.
+    fn is_zero(&self) -> bool;
+}
+
+impl<T> Zero for T
+where
+    T: num_traits::Zero,
+{
+    fn zero() -> Self {
+        <Self as num_traits::Zero>::zero()
+    }
+
+    fn is_zero(&self) -> bool {
+        <Self as num_traits::Zero>::is_zero(self)
+    }
+}
diff --git a/components/style/media_queries/media_feature_expression.rs b/components/style/media_queries/media_feature_expression.rs
index ec864510c72..6a9db93e889 100644
--- a/components/style/media_queries/media_feature_expression.rs
+++ b/components/style/media_queries/media_feature_expression.rs
@@ -21,9 +21,8 @@ use crate::stylesheets::Origin;
 use crate::values::computed::{self, ToComputedValue};
 use crate::values::specified::{Integer, Length, Number, Resolution};
 use crate::values::{serialize_atom_identifier, CSSFloat};
-use crate::Atom;
+use crate::{Atom, Zero};
 use cssparser::{Parser, Token};
-use num_traits::Zero;
 use std::cmp::{Ordering, PartialOrd};
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
diff --git a/components/style/properties/cascade.rs b/components/style/properties/cascade.rs
index 4a0e07fdcac..23970d64888 100644
--- a/components/style/properties/cascade.rs
+++ b/components/style/properties/cascade.rs
@@ -11,12 +11,13 @@ use crate::font_metrics::FontMetricsProvider;
 use crate::logical_geometry::WritingMode;
 use crate::media_queries::Device;
 use crate::properties::{ComputedValues, StyleBuilder};
-use crate::properties::{LonghandId, LonghandIdSet};
+use crate::properties::{LonghandId, LonghandIdSet, CSSWideKeyword};
 use crate::properties::{PropertyDeclaration, PropertyDeclarationId, DeclarationImportanceIterator};
 use crate::properties::CASCADE_PROPERTY;
 use crate::rule_cache::{RuleCache, RuleCacheConditions};
 use crate::rule_tree::{CascadeLevel, StrongRuleNode};
 use crate::selector_parser::PseudoElement;
+use crate::stylesheets::{Origin, PerOrigin};
 use servo_arc::Arc;
 use crate::shared_lock::StylesheetGuards;
 use smallbitvec::SmallBitVec;
@@ -251,7 +252,7 @@ where
         for (declaration, cascade_level) in iter_declarations() {
             declarations.push((declaration, cascade_level));
             if let PropertyDeclaration::Custom(ref declaration) = *declaration {
-                builder.cascade(&declaration.name, &declaration.value);
+                builder.cascade(declaration, cascade_level.origin());
             }
         }
 
@@ -339,14 +340,8 @@ fn should_ignore_declaration_when_ignoring_document_colors(
         return false;
     }
 
-    let is_ua_or_user_rule = matches!(
-        cascade_level,
-        CascadeLevel::UANormal |
-            CascadeLevel::UserNormal |
-            CascadeLevel::UserImportant |
-            CascadeLevel::UAImportant
-    );
-
+    let is_ua_or_user_rule =
+        matches!(cascade_level.origin(), Origin::User | Origin::UserAgent);
     if is_ua_or_user_rule {
         return false;
     }
@@ -388,6 +383,7 @@ struct Cascade<'a, 'b: 'a> {
     context: &'a mut computed::Context<'b>,
     cascade_mode: CascadeMode<'a>,
     seen: LonghandIdSet,
+    reverted: PerOrigin<LonghandIdSet>,
     saved_font_size: Option<PropertyDeclaration>,
     saved_font_family: Option<PropertyDeclaration>,
 }
@@ -398,6 +394,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
             context,
             cascade_mode,
             seen: LonghandIdSet::default(),
+            reverted: Default::default(),
             saved_font_size: None,
             saved_font_family: None,
         }
@@ -488,6 +485,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
 
         for (declaration, cascade_level) in declarations {
             let declaration_id = declaration.id();
+            let origin = cascade_level.origin();
             let longhand_id = match declaration_id {
                 PropertyDeclarationId::Longhand(id) => id,
                 PropertyDeclarationId::Custom(..) => continue,
@@ -513,6 +511,10 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
                 continue;
             }
 
+            if self.reverted.borrow_for_origin(&origin).contains(physical_longhand_id) {
+                continue;
+            }
+
             // Only a few properties are allowed to depend on the visited state
             // of links.  When cascading visited styles, we can save time by
             // only processing these properties.
@@ -540,8 +542,34 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
                 }
             }
 
+            let css_wide_keyword = declaration.get_css_wide_keyword();
+            if let Some(CSSWideKeyword::Revert) = css_wide_keyword {
+                // We intentionally don't want to insert it into `self.seen`,
+                // `reverted` takes care of rejecting other declarations as
+                // needed.
+                for origin in origin.following_including() {
+                    self.reverted
+                        .borrow_mut_for_origin(&origin)
+                        .insert(physical_longhand_id);
+                }
+                continue;
+            }
+
             self.seen.insert(physical_longhand_id);
 
+            let unset = css_wide_keyword.map_or(false, |css_wide_keyword| {
+                match css_wide_keyword {
+                    CSSWideKeyword::Unset => true,
+                    CSSWideKeyword::Inherit => inherited,
+                    CSSWideKeyword::Initial => !inherited,
+                    CSSWideKeyword::Revert => unreachable!(),
+                }
+            });
+
+            if unset {
+                continue;
+            }
+
             // FIXME(emilio): We should avoid generating code for logical
             // longhands and just use the physical ones, then rename
             // physical_longhand_id to just longhand_id.
@@ -800,18 +828,14 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
                     self.seen.contains(LonghandId::MozMinFontSizeRatio) ||
                     self.seen.contains(LonghandId::FontFamily)
                 {
-                    use crate::properties::{CSSWideKeyword, WideKeywordDeclaration};
+                    use crate::values::computed::FontSize;
 
                     // font-size must be explicitly inherited to handle lang
                     // changes and scriptlevel changes.
                     //
                     // FIXME(emilio): That looks a bit bogus...
-                    let inherit = PropertyDeclaration::CSSWideKeyword(WideKeywordDeclaration {
-                        id: LonghandId::FontSize,
-                        keyword: CSSWideKeyword::Inherit,
-                    });
-
-                    self.apply_declaration_ignoring_phase(LonghandId::FontSize, &inherit);
+                    self.context.for_non_inherited_property = None;
+                    FontSize::cascade_inherit_font_size(&mut self.context);
                 }
             }
         }
diff --git a/components/style/properties/data.py b/components/style/properties/data.py
index f3b4e43c225..9347d9b9428 100644
--- a/components/style/properties/data.py
+++ b/components/style/properties/data.py
@@ -347,6 +347,7 @@ class Longhand(object):
                 "TouchAction",
                 "TransformStyle",
                 "UserSelect",
+                "WordBreak",
                 "XSpan",
                 "XTextZoom",
                 "ZIndex",
diff --git a/components/style/properties/declaration_block.rs b/components/style/properties/declaration_block.rs
index d7058d99635..e4396e764a4 100644
--- a/components/style/properties/declaration_block.rs
+++ b/components/style/properties/declaration_block.rs
@@ -849,7 +849,7 @@ impl PropertyDeclarationBlock {
 
         for declaration in self.normal_declaration_iter() {
             if let PropertyDeclaration::Custom(ref declaration) = *declaration {
-                builder.cascade(&declaration.name, &declaration.value);
+                builder.cascade(declaration, Origin::Author);
             }
         }
 
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index b1be315e7a0..6a4d4d87a99 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -52,7 +52,7 @@ use crate::rule_tree::StrongRuleNode;
 use crate::selector_parser::PseudoElement;
 use servo_arc::{Arc, RawOffsetArc};
 use std::marker::PhantomData;
-use std::mem::{forget, uninitialized, transmute, zeroed};
+use std::mem::{forget, uninitialized, zeroed};
 use std::{cmp, ops, ptr};
 use crate::values::{self, CustomIdent, Either, KeyframesName, None_};
 use crate::values::computed::{NonNegativeLength, Percentage, TransitionProperty};
@@ -463,32 +463,27 @@ def set_gecko_property(ffi_name, expr):
     // set on mContextFlags, and the length field is set to the initial value.
 
     pub fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
-        use crate::values::generics::svg::{SVGLength, SvgLengthPercentageOrNumber};
+        use crate::values::generics::svg::SVGLength;
         use crate::gecko_bindings::structs::nsStyleSVG_${ident.upper()}_CONTEXT as CONTEXT_VALUE;
         let length = match v {
-            SVGLength::Length(length) => {
+            SVGLength::LengthPercentage(length) => {
                 self.gecko.mContextFlags &= !CONTEXT_VALUE;
                 length
             }
             SVGLength::ContextValue => {
                 self.gecko.mContextFlags |= CONTEXT_VALUE;
                 match longhands::${ident}::get_initial_value() {
-                    SVGLength::Length(length) => length,
+                    SVGLength::LengthPercentage(length) => length,
                     _ => unreachable!("Initial value should not be context-value"),
                 }
             }
         };
-        match length {
-            SvgLengthPercentageOrNumber::LengthPercentage(lp) =>
-                self.gecko.${gecko_ffi_name}.set(lp),
-            SvgLengthPercentageOrNumber::Number(num) =>
-                self.gecko.${gecko_ffi_name}.set_value(CoordDataValue::Factor(num.into())),
-        }
+        self.gecko.${gecko_ffi_name} = length;
     }
 
     pub fn copy_${ident}_from(&mut self, other: &Self) {
         use crate::gecko_bindings::structs::nsStyleSVG_${ident.upper()}_CONTEXT as CONTEXT_VALUE;
-        self.gecko.${gecko_ffi_name}.copy_from(&other.gecko.${gecko_ffi_name});
+        self.gecko.${gecko_ffi_name} = other.gecko.${gecko_ffi_name};
         self.gecko.mContextFlags =
             (self.gecko.mContextFlags & !CONTEXT_VALUE) |
             (other.gecko.mContextFlags & CONTEXT_VALUE);
@@ -499,32 +494,12 @@ def set_gecko_property(ffi_name, expr):
     }
 
     pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
-        use crate::values::generics::svg::{SVGLength, SvgLengthPercentageOrNumber};
-        use crate::values::computed::LengthPercentage;
+        use crate::values::generics::svg::SVGLength;
         use crate::gecko_bindings::structs::nsStyleSVG_${ident.upper()}_CONTEXT as CONTEXT_VALUE;
         if (self.gecko.mContextFlags & CONTEXT_VALUE) != 0 {
             return SVGLength::ContextValue;
         }
-        let length = match self.gecko.${gecko_ffi_name}.as_value() {
-            CoordDataValue::Factor(number) => {
-                SvgLengthPercentageOrNumber::Number(number)
-            },
-            CoordDataValue::Coord(coord) => {
-                SvgLengthPercentageOrNumber::LengthPercentage(
-                    LengthPercentage::new(Au(coord).into(), None)
-                )
-            },
-            CoordDataValue::Percent(p) => {
-                SvgLengthPercentageOrNumber::LengthPercentage(
-                    LengthPercentage::new(Au(0).into(), Some(Percentage(p)))
-                )
-            },
-            CoordDataValue::Calc(calc) => {
-                SvgLengthPercentageOrNumber::LengthPercentage(calc.into())
-            },
-            _ => unreachable!("Unexpected coordinate in ${ident}"),
-        };
-        SVGLength::Length(length.into())
+        SVGLength::LengthPercentage(self.gecko.${gecko_ffi_name})
     }
 </%def>
 
@@ -817,34 +792,23 @@ def set_gecko_property(ffi_name, expr):
     }
 </%def>
 
-<%def name="impl_corner_style_coord(ident, gecko_ffi_name, x_index, y_index)">
+<%def name="impl_corner_style_coord(ident, gecko_ffi_name, corner)">
     #[allow(non_snake_case)]
     pub fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
-        v.0.width().to_gecko_style_coord(&mut self.gecko.${gecko_ffi_name}.data_at_mut(${x_index}));
-        v.0.height().to_gecko_style_coord(&mut self.gecko.${gecko_ffi_name}.data_at_mut(${y_index}));
+        self.gecko.${gecko_ffi_name}.${corner} = v;
     }
     #[allow(non_snake_case)]
     pub fn copy_${ident}_from(&mut self, other: &Self) {
-        self.gecko.${gecko_ffi_name}.data_at_mut(${x_index})
-                  .copy_from(&other.gecko.${gecko_ffi_name}.data_at(${x_index}));
-        self.gecko.${gecko_ffi_name}.data_at_mut(${y_index})
-                  .copy_from(&other.gecko.${gecko_ffi_name}.data_at(${y_index}));
+        self.gecko.${gecko_ffi_name}.${corner} =
+            other.gecko.${gecko_ffi_name}.${corner};
     }
     #[allow(non_snake_case)]
     pub fn reset_${ident}(&mut self, other: &Self) {
         self.copy_${ident}_from(other)
     }
-
     #[allow(non_snake_case)]
     pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
-        use crate::values::computed::border::BorderCornerRadius;
-        let width = GeckoStyleCoordConvertible::from_gecko_style_coord(
-                        &self.gecko.${gecko_ffi_name}.data_at(${x_index}))
-                        .expect("Failed to clone ${ident}");
-        let height = GeckoStyleCoordConvertible::from_gecko_style_coord(
-                        &self.gecko.${gecko_ffi_name}.data_at(${y_index}))
-                        .expect("Failed to clone ${ident}");
-        BorderCornerRadius::new(width, height)
+        self.gecko.${gecko_ffi_name}.${corner}
     }
 </%def>
 
@@ -891,13 +855,13 @@ def set_gecko_property(ffi_name, expr):
 transform_functions = [
     ("Matrix3D", "matrix3d", ["number"] * 16),
     ("Matrix", "matrix", ["number"] * 6),
-    ("Translate", "translate", ["lp", "optional_lp"]),
+    ("Translate", "translate", ["lp", "lp"]),
     ("Translate3D", "translate3d", ["lp", "lp", "length"]),
     ("TranslateX", "translatex", ["lp"]),
     ("TranslateY", "translatey", ["lp"]),
     ("TranslateZ", "translatez", ["length"]),
     ("Scale3D", "scale3d", ["number"] * 3),
-    ("Scale", "scale", ["number", "optional_number"]),
+    ("Scale", "scale", ["number", "number"]),
     ("ScaleX", "scalex", ["number"]),
     ("ScaleY", "scaley", ["number"]),
     ("ScaleZ", "scalez", ["number"]),
@@ -906,7 +870,7 @@ transform_functions = [
     ("RotateX", "rotatex", ["angle"]),
     ("RotateY", "rotatey", ["angle"]),
     ("RotateZ", "rotatez", ["angle"]),
-    ("Skew", "skew", ["angle", "optional_angle"]),
+    ("Skew", "skew", ["angle", "angle"]),
     ("SkewX", "skewx", ["angle"]),
     ("SkewY", "skewy", ["angle"]),
     ("Perspective", "perspective", ["length"]),
@@ -917,7 +881,6 @@ transform_functions = [
 
 <%def name="transform_function_arm(name, keyword, items)">
     <%
-        has_optional = items[-1].startswith("optional_")
         pattern = None
         if keyword == "matrix3d":
             # m11: number1, m12: number2, ..
@@ -955,36 +918,20 @@ transform_functions = [
         }
     %>
     crate::values::generics::transform::TransformOperation::${name}${pattern} => {
-        % if has_optional:
-            let optional_present = ${items[-1] + str(len(items))}.is_some();
-            let len = if optional_present {
-                ${len(items) + 1}
-            } else {
-                ${len(items)}
-            };
-        % else:
-            let len = ${len(items) + 1};
-        % endif
+        let len = ${len(items) + 1};
         bindings::Gecko_CSSValue_SetFunction(gecko_value, len);
         bindings::Gecko_CSSValue_SetKeyword(
             bindings::Gecko_CSSValue_GetArrayItem(gecko_value, 0),
             structs::nsCSSKeyword::eCSSKeyword_${keyword}
         );
         % for index, item in enumerate(items):
-            <% replaced_item = item.replace("optional_", "") %>
-            % if item.startswith("optional"):
-                if let Some(${replaced_item + str(index + 1)}) = ${item + str(index + 1)} {
-            % endif
             % if item == "list":
                 debug_assert!(!${item}${index + 1}.0.is_empty());
             % endif
-            ${css_value_setters[replaced_item] % (
+            ${css_value_setters[item] % (
                 "bindings::Gecko_CSSValue_GetArrayItem(gecko_value, %d)" % (index + 1),
-                replaced_item + str(index + 1)
+                item + str(index + 1)
             )};
-            % if item.startswith("optional"):
-                }
-            % endif
         % endfor
     }
 </%def>
@@ -995,8 +942,6 @@ transform_functions = [
         css_value_getters = {
             "length" : "Length::new(bindings::Gecko_CSSValue_GetNumber(%s))",
             "lp" : "%s.get_length_percentage()",
-            "lpon" : "Either::Second(%s.get_length_percentage())",
-            "lon" : "Either::First(%s.get_length())",
             "angle" : "%s.get_angle()",
             "number" : "bindings::Gecko_CSSValue_GetNumber(%s)",
             "percentage" : "Percentage(bindings::Gecko_CSSValue_GetPercentage(%s))",
@@ -1034,20 +979,11 @@ transform_functions = [
                 ${field_names[index]}:
             % endif
             <%
-                getter = css_value_getters[item.replace("optional_", "")] % (
+                getter = css_value_getters[item] % (
                     "bindings::Gecko_CSSValue_GetArrayItemConst(gecko_value, %d)" % (index + 1)
                 )
             %>
-            % if item.startswith("optional_"):
-                if (**gecko_value.mValue.mArray.as_ref()).mCount == ${index + 1} {
-                    None
-                } else {
-                    Some(${getter})
-                }
-            % else:
-                ${getter}
-            % endif
-,
+            ${getter},
         % endfor
         ${post_symbols}
     },
@@ -1291,55 +1227,23 @@ impl Clone for ${style_struct.gecko_struct_name} {
 
     # Types used with predefined_type()-defined properties that we can auto-generate.
     predefined_types = {
-        "Appearance": impl_simple,
-        "OverscrollBehavior": impl_simple,
-        "OverflowClipBox": impl_simple,
-        "ScrollSnapAlign": impl_simple,
-        "ScrollSnapType": impl_simple,
-        "Float": impl_simple,
-        "Overflow": impl_simple,
-        "BreakBetween": impl_simple,
-        "BreakWithin": impl_simple,
-        "Resize": impl_simple,
         "Color": impl_color,
         "ColorOrAuto": impl_color,
-        "GreaterThanOrEqualToOneNumber": impl_simple,
-        "Integer": impl_simple,
         "length::LengthOrAuto": impl_style_coord,
         "length::LengthOrNormal": impl_style_coord,
         "length::NonNegativeLengthOrAuto": impl_style_coord,
         "length::NonNegativeLengthPercentageOrNormal": impl_style_coord,
-        "FillRule": impl_simple,
-        "FlexBasis": impl_simple,
         "Length": impl_absolute_length,
         "LengthOrNormal": impl_style_coord,
-        "LengthPercentage": impl_simple,
         "LengthPercentageOrAuto": impl_style_coord,
-        "MaxSize": impl_simple,
-        "Size": impl_simple,
         "MozScriptMinSize": impl_absolute_length,
-        "MozScriptSizeMultiplier": impl_simple,
-        "NonNegativeLengthPercentage": impl_simple,
-        "NonNegativeLengthOrNumber": impl_simple,
-        "NonNegativeLengthOrNumberRect": impl_simple,
-        "BorderImageSlice": impl_simple,
-        "NonNegativeNumber": impl_simple,
-        "Number": impl_simple,
-        "Opacity": impl_simple,
-        "OverflowWrap": impl_simple,
-        "OverflowAnchor": impl_simple,
-        "Perspective": impl_simple,
-        "Position": impl_simple,
         "RGBAColor": impl_rgba_color,
         "SVGLength": impl_svg_length,
         "SVGOpacity": impl_svg_opacity,
         "SVGPaint": impl_svg_paint,
         "SVGWidth": impl_svg_length,
         "Transform": impl_transform,
-        "TransformOrigin": impl_simple,
-        "UserSelect": impl_simple,
         "url::UrlOrNone": impl_css_url,
-        "ZIndex": impl_simple,
     }
 
     def longhand_method(longhand):
@@ -1354,15 +1258,12 @@ impl Clone for ${style_struct.gecko_struct_name} {
             args.update(keyword=longhand.keyword)
             if "font" in longhand.ident:
                 args.update(cast_type=longhand.cast_type)
-        else:
+        elif longhand.predefined_type in predefined_types:
             method = predefined_types[longhand.predefined_type]
+        else:
+            method = impl_simple
 
         method(**args)
-
-    picked_longhands = []
-    for x in longhands:
-        if x.keyword or x.predefined_type in predefined_types or x.logical:
-            picked_longhands.append(x)
 %>
 impl ${style_struct.gecko_struct_name} {
     /*
@@ -1374,7 +1275,7 @@ impl ${style_struct.gecko_struct_name} {
      * Auto-Generated Methods.
      */
     <%
-    for longhand in picked_longhands:
+    for longhand in longhands:
         longhand_method(longhand)
     %>
 }
@@ -1387,14 +1288,6 @@ class Side(object):
         self.ident = name.lower()
         self.index = index
 
-class Corner(object):
-    def __init__(self, vert, horiz, index):
-        self.x_name = "HalfCorner::eCorner" + vert + horiz + "X"
-        self.y_name = "HalfCorner::eCorner" + vert + horiz + "Y"
-        self.ident = (vert + "_" + horiz).lower()
-        self.x_index = 2 * index
-        self.y_index = 2 * index + 1
-
 class GridLine(object):
     def __init__(self, name):
         self.ident = "grid-" + name.lower()
@@ -1402,19 +1295,12 @@ class GridLine(object):
         self.gecko = "m" + to_camel_case(self.ident)
 
 SIDES = [Side("Top", 0), Side("Right", 1), Side("Bottom", 2), Side("Left", 3)]
-CORNERS = [Corner("Top", "Left", 0), Corner("Top", "Right", 1),
-           Corner("Bottom", "Right", 2), Corner("Bottom", "Left", 3)]
+CORNERS = ["top_left", "top_right", "bottom_right", "bottom_left"]
 GRID_LINES = map(GridLine, ["row-start", "row-end", "column-start", "column-end"])
 %>
 
 #[allow(dead_code)]
 fn static_assert() {
-    unsafe {
-        % for corner in CORNERS:
-        transmute::<_, [u32; ${corner.x_index}]>([1; structs::${corner.x_name} as usize]);
-        transmute::<_, [u32; ${corner.y_index}]>([1; structs::${corner.y_name} as usize]);
-        % endfor
-    }
     // Note: using the above technique with an enum hits a rust bug when |structs| is in a different crate.
     % for side in SIDES:
     { const DETAIL: u32 = [0][(structs::Side::eSide${side.name} as usize != ${side.index}) as usize]; let _ = DETAIL; }
@@ -1425,7 +1311,7 @@ fn static_assert() {
 <% skip_border_longhands = " ".join(["border-{0}-{1}".format(x.ident, y)
                                      for x in SIDES
                                      for y in ["color", "style", "width"]] +
-                                    ["border-{0}-radius".format(x.ident.replace("_", "-"))
+                                    ["border-{0}-radius".format(x.replace("_", "-"))
                                      for x in CORNERS]) %>
 
 <%self:impl_trait style_struct_name="Border"
@@ -1494,10 +1380,9 @@ fn static_assert() {
     % endfor
 
     % for corner in CORNERS:
-    <% impl_corner_style_coord("border_%s_radius" % corner.ident,
+    <% impl_corner_style_coord("border_%s_radius" % corner,
                                "mBorderRadius",
-                               corner.x_index,
-                               corner.y_index) %>
+                               corner) %>
     % endfor
 
     pub fn set_border_image_source(&mut self, image: longhands::border_image_source::computed_value::T) {
@@ -2027,7 +1912,7 @@ fn static_assert() {
 </%self:impl_trait>
 
 <% skip_outline_longhands = " ".join("outline-style outline-width".split() +
-                                     ["-moz-outline-radius-{0}".format(x.ident.replace("_", ""))
+                                     ["-moz-outline-radius-{0}".format(x.replace("_", ""))
                                       for x in CORNERS]) %>
 <%self:impl_trait style_struct_name="Outline"
                   skip_longhands="${skip_outline_longhands}">
@@ -2059,10 +1944,9 @@ fn static_assert() {
                                 round_to_pixels=True) %>
 
     % for corner in CORNERS:
-    <% impl_corner_style_coord("_moz_outline_radius_%s" % corner.ident.replace("_", ""),
+    <% impl_corner_style_coord("_moz_outline_radius_%s" % corner.replace("_", ""),
                                "mOutlineRadius",
-                               corner.x_index,
-                               corner.y_index) %>
+                               corner) %>
     % endfor
 
     pub fn outline_has_nonzero_width(&self) -> bool {
@@ -2072,6 +1956,7 @@ fn static_assert() {
 
 <%
     skip_font_longhands = """font-family font-size font-size-adjust font-weight
+                             font-style font-stretch -moz-script-level
                              font-synthesis -x-lang font-variant-alternates
                              font-variant-east-asian font-variant-ligatures
                              font-variant-numeric font-language-override
@@ -2863,6 +2748,7 @@ fn static_assert() {
                           animation-iteration-count animation-timing-function
                           clear transition-duration transition-delay
                           transition-timing-function transition-property
+                          transform-style
                           rotate scroll-snap-points-x scroll-snap-points-y
                           scroll-snap-coordinate -moz-binding will-change
                           offset-path shape-outside contain touch-action
@@ -3291,7 +3177,6 @@ fn static_assert() {
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_CONTENT;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_SIZE;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_LAYOUT;
-        use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_STYLE;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_PAINT;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_ALL_BITS;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_CONTENT_BITS;
@@ -3315,9 +3200,6 @@ fn static_assert() {
         if v.contains(SpecifiedValue::LAYOUT) {
             bitfield |= NS_STYLE_CONTAIN_LAYOUT;
         }
-        if v.contains(SpecifiedValue::STYLE) {
-            bitfield |= NS_STYLE_CONTAIN_STYLE;
-        }
         if v.contains(SpecifiedValue::PAINT) {
             bitfield |= NS_STYLE_CONTAIN_PAINT;
         }
@@ -3333,7 +3215,6 @@ fn static_assert() {
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_CONTENT;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_SIZE;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_LAYOUT;
-        use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_STYLE;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_PAINT;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_ALL_BITS;
         use crate::gecko_bindings::structs::NS_STYLE_CONTAIN_CONTENT_BITS;
@@ -3363,9 +3244,6 @@ fn static_assert() {
         if gecko_flags & (NS_STYLE_CONTAIN_LAYOUT as u8) != 0 {
             servo_flags.insert(SpecifiedValue::LAYOUT);
         }
-        if gecko_flags & (NS_STYLE_CONTAIN_STYLE as u8) != 0 {
-            servo_flags.insert(SpecifiedValue::STYLE);
-        }
         if gecko_flags & (NS_STYLE_CONTAIN_PAINT as u8) != 0 {
             servo_flags.insert(SpecifiedValue::PAINT);
         }
@@ -3870,6 +3748,7 @@ fn static_assert() {
     #[allow(non_snake_case)]
     pub fn set__moz_image_region(&mut self, v: longhands::_moz_image_region::computed_value::T) {
         use crate::values::Either;
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
 
         match v {
             Either::Second(_auto) => {
@@ -3879,15 +3758,21 @@ fn static_assert() {
                 self.gecko.mImageRegion.height = 0;
             }
             Either::First(rect) => {
-                self.gecko.mImageRegion.x = rect.left.map(Au::from).unwrap_or(Au(0)).0;
-                self.gecko.mImageRegion.y = rect.top.map(Au::from).unwrap_or(Au(0)).0;
+                self.gecko.mImageRegion.x = match rect.left {
+                    LengthPercentage(v) => v.to_i32_au(),
+                    Auto => 0,
+                };
+                self.gecko.mImageRegion.y = match rect.top {
+                    LengthPercentage(v) => v.to_i32_au(),
+                    Auto => 0,
+                };
                 self.gecko.mImageRegion.height = match rect.bottom {
-                    Some(value) => (Au::from(value) - Au(self.gecko.mImageRegion.y)).0,
-                    None => 0,
+                    LengthPercentage(value) => (Au::from(value) - Au(self.gecko.mImageRegion.y)).0,
+                    Auto => 0,
                 };
                 self.gecko.mImageRegion.width = match rect.right {
-                    Some(value) => (Au::from(value) - Au(self.gecko.mImageRegion.x)).0,
-                    None => 0,
+                    LengthPercentage(value) => (Au::from(value) - Au(self.gecko.mImageRegion.x)).0,
+                    Auto => 0,
                 };
             }
         }
@@ -3896,6 +3781,7 @@ fn static_assert() {
     #[allow(non_snake_case)]
     pub fn clone__moz_image_region(&self) -> longhands::_moz_image_region::computed_value::T {
         use crate::values::{Auto, Either};
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
         use crate::values::computed::ClipRect;
 
         // There is no ideal way to detect auto type for structs::nsRect and its components, so
@@ -3908,10 +3794,10 @@ fn static_assert() {
         }
 
         Either::First(ClipRect {
-            top: Some(Au(self.gecko.mImageRegion.y).into()),
-            right: Some(Au(self.gecko.mImageRegion.width + self.gecko.mImageRegion.x).into()),
-            bottom: Some(Au(self.gecko.mImageRegion.height + self.gecko.mImageRegion.y).into()),
-            left: Some(Au(self.gecko.mImageRegion.x).into()),
+            top: LengthPercentage(Au(self.gecko.mImageRegion.y).into()),
+            right: LengthPercentage(Au(self.gecko.mImageRegion.width + self.gecko.mImageRegion.x).into()),
+            bottom: LengthPercentage(Au(self.gecko.mImageRegion.height + self.gecko.mImageRegion.y).into()),
+            left: LengthPercentage(Au(self.gecko.mImageRegion.x).into()),
         })
     }
 
@@ -3968,38 +3854,43 @@ fn static_assert() {
         use crate::gecko_bindings::structs::NS_STYLE_CLIP_TOP_AUTO;
         use crate::gecko_bindings::structs::NS_STYLE_CLIP_RIGHT_AUTO;
         use crate::gecko_bindings::structs::NS_STYLE_CLIP_BOTTOM_AUTO;
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
         use crate::values::Either;
 
         match v {
             Either::First(rect) => {
                 self.gecko.mClipFlags = NS_STYLE_CLIP_RECT as u8;
-                if let Some(left) = rect.left {
-                    self.gecko.mClip.x = left.to_i32_au();
-                } else {
-                    self.gecko.mClip.x = 0;
-                    self.gecko.mClipFlags |= NS_STYLE_CLIP_LEFT_AUTO as u8;
-                }
+                self.gecko.mClip.x = match rect.left {
+                    LengthPercentage(l) => l.to_i32_au(),
+                    Auto => {
+                        self.gecko.mClipFlags |= NS_STYLE_CLIP_LEFT_AUTO as u8;
+                        0
+                    }
+                };
 
-                if let Some(top) = rect.top {
-                    self.gecko.mClip.y = top.to_i32_au();
-                } else {
-                    self.gecko.mClip.y = 0;
-                    self.gecko.mClipFlags |= NS_STYLE_CLIP_TOP_AUTO as u8;
-                }
+                self.gecko.mClip.y = match rect.top {
+                    LengthPercentage(l) => l.to_i32_au(),
+                    Auto => {
+                        self.gecko.mClipFlags |= NS_STYLE_CLIP_TOP_AUTO as u8;
+                        0
+                    }
+                };
 
-                if let Some(bottom) = rect.bottom {
-                    self.gecko.mClip.height = (Au::from(bottom) - Au(self.gecko.mClip.y)).0;
-                } else {
-                    self.gecko.mClip.height = 1 << 30; // NS_MAXSIZE
-                    self.gecko.mClipFlags |= NS_STYLE_CLIP_BOTTOM_AUTO as u8;
-                }
+                self.gecko.mClip.height = match rect.bottom {
+                    LengthPercentage(l) => (Au::from(l) - Au(self.gecko.mClip.y)).0,
+                    Auto => {
+                        self.gecko.mClipFlags |= NS_STYLE_CLIP_BOTTOM_AUTO as u8;
+                        1 << 30 // NS_MAXSIZE
+                    }
+                };
 
-                if let Some(right) = rect.right {
-                    self.gecko.mClip.width = (Au::from(right) - Au(self.gecko.mClip.x)).0;
-                } else {
-                    self.gecko.mClip.width = 1 << 30; // NS_MAXSIZE
-                    self.gecko.mClipFlags |= NS_STYLE_CLIP_RIGHT_AUTO as u8;
-                }
+                self.gecko.mClip.width = match rect.right {
+                    LengthPercentage(l) => (Au::from(l) - Au(self.gecko.mClip.x)).0,
+                    Auto => {
+                        self.gecko.mClipFlags |= NS_STYLE_CLIP_RIGHT_AUTO as u8;
+                        1 << 30 // NS_MAXSIZE
+                    }
+                };
             },
             Either::Second(_auto) => {
                 self.gecko.mClipFlags = NS_STYLE_CLIP_AUTO as u8;
@@ -4026,42 +3917,42 @@ fn static_assert() {
         use crate::gecko_bindings::structs::NS_STYLE_CLIP_LEFT_AUTO;
         use crate::gecko_bindings::structs::NS_STYLE_CLIP_RIGHT_AUTO;
         use crate::gecko_bindings::structs::NS_STYLE_CLIP_TOP_AUTO;
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
         use crate::values::computed::{ClipRect, ClipRectOrAuto};
         use crate::values::Either;
 
         if self.gecko.mClipFlags == NS_STYLE_CLIP_AUTO as u8 {
-            ClipRectOrAuto::auto()
+            return ClipRectOrAuto::auto()
+        }
+        let left = if self.gecko.mClipFlags & NS_STYLE_CLIP_LEFT_AUTO as u8 != 0 {
+            debug_assert_eq!(self.gecko.mClip.x, 0);
+            Auto
         } else {
-            let left = if self.gecko.mClipFlags & NS_STYLE_CLIP_LEFT_AUTO as u8 != 0 {
-                debug_assert_eq!(self.gecko.mClip.x, 0);
-                None
-            } else {
-                Some(Au(self.gecko.mClip.x).into())
-            };
+            LengthPercentage(Au(self.gecko.mClip.x).into())
+        };
 
-            let top = if self.gecko.mClipFlags & NS_STYLE_CLIP_TOP_AUTO as u8 != 0 {
-                debug_assert_eq!(self.gecko.mClip.y, 0);
-                None
-            } else {
-                Some(Au(self.gecko.mClip.y).into())
-            };
+        let top = if self.gecko.mClipFlags & NS_STYLE_CLIP_TOP_AUTO as u8 != 0 {
+            debug_assert_eq!(self.gecko.mClip.y, 0);
+            Auto
+        } else {
+            LengthPercentage(Au(self.gecko.mClip.y).into())
+        };
 
-            let bottom = if self.gecko.mClipFlags & NS_STYLE_CLIP_BOTTOM_AUTO as u8 != 0 {
-                debug_assert_eq!(self.gecko.mClip.height, 1 << 30); // NS_MAXSIZE
-                None
-            } else {
-                Some(Au(self.gecko.mClip.y + self.gecko.mClip.height).into())
-            };
+        let bottom = if self.gecko.mClipFlags & NS_STYLE_CLIP_BOTTOM_AUTO as u8 != 0 {
+            debug_assert_eq!(self.gecko.mClip.height, 1 << 30); // NS_MAXSIZE
+            Auto
+        } else {
+            LengthPercentage(Au(self.gecko.mClip.y + self.gecko.mClip.height).into())
+        };
 
-            let right = if self.gecko.mClipFlags & NS_STYLE_CLIP_RIGHT_AUTO as u8 != 0 {
-                debug_assert_eq!(self.gecko.mClip.width, 1 << 30); // NS_MAXSIZE
-                None
-            } else {
-                Some(Au(self.gecko.mClip.x + self.gecko.mClip.width).into())
-            };
+        let right = if self.gecko.mClipFlags & NS_STYLE_CLIP_RIGHT_AUTO as u8 != 0 {
+            debug_assert_eq!(self.gecko.mClip.width, 1 << 30); // NS_MAXSIZE
+            Auto
+        } else {
+            LengthPercentage(Au(self.gecko.mClip.x + self.gecko.mClip.width).into())
+        };
 
-            Either::First(ClipRect { top, right, bottom, left })
-        }
+        Either::First(ClipRect { top, right, bottom, left })
     }
 
     <%
@@ -4238,7 +4129,7 @@ fn static_assert() {
 
 
 <%self:impl_trait style_struct_name="InheritedText"
-                  skip_longhands="text-align text-emphasis-style text-shadow line-height letter-spacing word-spacing
+                  skip_longhands="text-align text-emphasis-style text-shadow
                                   -webkit-text-stroke-width text-emphasis-position">
 
     <% text_align_keyword = Keyword("text-align",
@@ -4270,78 +4161,6 @@ fn static_assert() {
         longhands::text_shadow::computed_value::List(buf)
     }
 
-    pub fn set_line_height(&mut self, v: longhands::line_height::computed_value::T) {
-        use crate::values::generics::text::LineHeight;
-        // FIXME: Align binary representations and ditch |match| for cast + static_asserts
-        let en = match v {
-            LineHeight::Normal => CoordDataValue::Normal,
-            LineHeight::Length(val) => CoordDataValue::Coord(val.0.to_i32_au()),
-            LineHeight::Number(val) => CoordDataValue::Factor(val.0),
-            LineHeight::MozBlockHeight =>
-                    CoordDataValue::Enumerated(structs::NS_STYLE_LINE_HEIGHT_BLOCK_HEIGHT),
-        };
-        self.gecko.mLineHeight.set_value(en);
-    }
-
-    pub fn clone_line_height(&self) -> longhands::line_height::computed_value::T {
-        use crate::values::generics::text::LineHeight;
-        return match self.gecko.mLineHeight.as_value() {
-            CoordDataValue::Normal => LineHeight::Normal,
-            CoordDataValue::Coord(coord) => LineHeight::Length(Au(coord).into()),
-            CoordDataValue::Factor(n) => LineHeight::Number(n.into()),
-            CoordDataValue::Enumerated(val) if val == structs::NS_STYLE_LINE_HEIGHT_BLOCK_HEIGHT =>
-                LineHeight::MozBlockHeight,
-            _ => panic!("this should not happen"),
-        }
-    }
-
-    <%call expr="impl_coord_copy('line_height', 'mLineHeight')"></%call>
-
-    pub fn set_letter_spacing(&mut self, v: longhands::letter_spacing::computed_value::T) {
-        use crate::values::generics::text::Spacing;
-        match v {
-            Spacing::Value(value) => self.gecko.mLetterSpacing.set(value),
-            Spacing::Normal => self.gecko.mLetterSpacing.set_value(CoordDataValue::Normal)
-        }
-    }
-
-    pub fn clone_letter_spacing(&self) -> longhands::letter_spacing::computed_value::T {
-        use crate::values::computed::Length;
-        use crate::values::generics::text::Spacing;
-        debug_assert!(
-            matches!(self.gecko.mLetterSpacing.as_value(),
-                     CoordDataValue::Normal |
-                     CoordDataValue::Coord(_)),
-            "Unexpected computed value for letter-spacing");
-        Length::from_gecko_style_coord(&self.gecko.mLetterSpacing).map_or(Spacing::Normal, Spacing::Value)
-    }
-
-    <%call expr="impl_coord_copy('letter_spacing', 'mLetterSpacing')"></%call>
-
-    pub fn set_word_spacing(&mut self, v: longhands::word_spacing::computed_value::T) {
-        use crate::values::generics::text::Spacing;
-        match v {
-            Spacing::Value(lp) => self.gecko.mWordSpacing.set(lp),
-            // https://drafts.csswg.org/css-text-3/#valdef-word-spacing-normal
-            Spacing::Normal => self.gecko.mWordSpacing.set_value(CoordDataValue::Coord(0)),
-        }
-    }
-
-    pub fn clone_word_spacing(&self) -> longhands::word_spacing::computed_value::T {
-        use crate::values::computed::LengthPercentage;
-        use crate::values::generics::text::Spacing;
-        debug_assert!(
-            matches!(self.gecko.mWordSpacing.as_value(),
-                     CoordDataValue::Normal |
-                     CoordDataValue::Coord(_) |
-                     CoordDataValue::Percent(_) |
-                     CoordDataValue::Calc(_)),
-            "Unexpected computed value for word-spacing");
-        LengthPercentage::from_gecko_style_coord(&self.gecko.mWordSpacing).map_or(Spacing::Normal, Spacing::Value)
-    }
-
-    <%call expr="impl_coord_copy('word_spacing', 'mWordSpacing')"></%call>
-
     fn clear_text_emphasis_style_if_string(&mut self) {
         if self.gecko.mTextEmphasisStyle == structs::NS_STYLE_TEXT_EMPHASIS_STYLE_STRING as u8 {
             self.gecko.mTextEmphasisStyleString.truncate();
@@ -4593,7 +4412,6 @@ fn set_style_svg_path(
         use crate::gecko_bindings::bindings::{Gecko_NewBasicShape, Gecko_DestroyShapeSource};
         use crate::gecko_bindings::structs::{StyleBasicShape, StyleBasicShapeType, StyleShapeSourceType};
         use crate::gecko_bindings::structs::{StyleGeometryBox, StyleShapeSource};
-        use crate::gecko::conversions::basic_shape::set_corners_from_radius;
         use crate::gecko::values::GeckoStyleCoordConvertible;
         use crate::values::generics::basic_shape::{BasicShape, ShapeSource};
 
@@ -4658,8 +4476,7 @@ fn set_style_svg_path(
                         inset.rect.2.to_gecko_style_coord(&mut shape.mCoordinates[2]);
                         shape.mCoordinates[3].leaky_set_null();
                         inset.rect.3.to_gecko_style_coord(&mut shape.mCoordinates[3]);
-
-                        set_corners_from_radius(inset.round, &mut shape.mRadius);
+                        shape.mRadius = inset.round;
                     }
                     BasicShape::Circle(circ) => {
                         let shape = init_shape(${ident}, StyleBasicShapeType::Circle);
@@ -4747,7 +4564,7 @@ clip-path
 
     pub fn set_stroke_dasharray(&mut self, v: longhands::stroke_dasharray::computed_value::T) {
         use crate::gecko_bindings::structs::nsStyleSVG_STROKE_DASHARRAY_CONTEXT as CONTEXT_VALUE;
-        use crate::values::generics::svg::{SVGStrokeDashArray, SvgLengthPercentageOrNumber};
+        use crate::values::generics::svg::SVGStrokeDashArray;
 
         match v {
             SVGStrokeDashArray::Values(v) => {
@@ -4757,12 +4574,7 @@ clip-path
                     bindings::Gecko_nsStyleSVG_SetDashArrayLength(&mut self.gecko, v.len() as u32);
                 }
                 for (gecko, servo) in self.gecko.mStrokeDasharray.iter_mut().zip(v) {
-                    match servo {
-                        SvgLengthPercentageOrNumber::LengthPercentage(lp) =>
-                            gecko.set(lp),
-                        SvgLengthPercentageOrNumber::Number(num) =>
-                            gecko.set_value(CoordDataValue::Factor(num.into())),
-                    }
+                    *gecko = servo;
                 }
             }
             SVGStrokeDashArray::ContextValue => {
@@ -4790,32 +4602,13 @@ clip-path
 
     pub fn clone_stroke_dasharray(&self) -> longhands::stroke_dasharray::computed_value::T {
         use crate::gecko_bindings::structs::nsStyleSVG_STROKE_DASHARRAY_CONTEXT as CONTEXT_VALUE;
-        use crate::values::computed::LengthPercentage;
-        use crate::values::generics::NonNegative;
-        use crate::values::generics::svg::{SVGStrokeDashArray, SvgLengthPercentageOrNumber};
+        use crate::values::generics::svg::SVGStrokeDashArray;
 
         if self.gecko.mContextFlags & CONTEXT_VALUE != 0 {
             debug_assert_eq!(self.gecko.mStrokeDasharray.len(), 0);
             return SVGStrokeDashArray::ContextValue;
         }
-        let mut vec = vec![];
-        for gecko in self.gecko.mStrokeDasharray.iter() {
-            match gecko.as_value() {
-                CoordDataValue::Factor(number) =>
-                    vec.push(SvgLengthPercentageOrNumber::Number(number.into())),
-                CoordDataValue::Coord(coord) =>
-                    vec.push(SvgLengthPercentageOrNumber::LengthPercentage(
-                        NonNegative(LengthPercentage::new(Au(coord).into(), None).into()))),
-                CoordDataValue::Percent(p) =>
-                    vec.push(SvgLengthPercentageOrNumber::LengthPercentage(
-                        NonNegative(LengthPercentage::new_percent(Percentage(p)).into()))),
-                CoordDataValue::Calc(calc) =>
-                    vec.push(SvgLengthPercentageOrNumber::LengthPercentage(
-                        NonNegative(LengthPercentage::from(calc).clamp_to_non_negative()))),
-                _ => unreachable!(),
-            }
-        }
-        SVGStrokeDashArray::Values(vec)
+        SVGStrokeDashArray::Values(self.gecko.mStrokeDasharray.iter().cloned().collect())
     }
 
     #[allow(non_snake_case)]
diff --git a/components/style/properties/helpers.mako.rs b/components/style/properties/helpers.mako.rs
index 59c9785292c..81931bc713b 100644
--- a/components/style/properties/helpers.mako.rs
+++ b/components/style/properties/helpers.mako.rs
@@ -19,6 +19,8 @@
         #[allow(unused_imports)]
         use crate::values::specified::AllowQuirks;
         #[allow(unused_imports)]
+        use crate::Zero;
+        #[allow(unused_imports)]
         use smallvec::SmallVec;
         pub use crate::values::specified::${type} as SpecifiedValue;
         pub mod computed_value {
@@ -324,29 +326,32 @@
                 PropertyDeclaration::CSSWideKeyword(ref declaration) => {
                     debug_assert_eq!(declaration.id, LonghandId::${property.camel_case});
                     match declaration.keyword {
-                        % if not data.current_style_struct.inherited:
+                        % if not property.style_struct.inherited:
                         CSSWideKeyword::Unset |
                         % endif
                         CSSWideKeyword::Initial => {
-                            % if property.ident == "font_size":
-                                computed::FontSize::cascade_initial_font_size(context);
+                            % if not property.style_struct.inherited:
+                                debug_assert!(false, "Should be handled in apply_properties");
                             % else:
+                                % if property.name == "font-size":
+                                computed::FontSize::cascade_initial_font_size(context);
+                                % else:
                                 context.builder.reset_${property.ident}();
+                                % endif
                             % endif
                         },
-                        % if data.current_style_struct.inherited:
+                        % if property.style_struct.inherited:
                         CSSWideKeyword::Unset |
                         % endif
                         CSSWideKeyword::Inherit => {
-                            % if not property.style_struct.inherited:
-                                context.rule_cache_conditions.borrow_mut().set_uncacheable();
-                            % endif
-                            % if property.ident == "font_size":
-                                computed::FontSize::cascade_inherit_font_size(context);
+                            % if property.style_struct.inherited:
+                                debug_assert!(false, "Should be handled in apply_properties");
                             % else:
+                                context.rule_cache_conditions.borrow_mut().set_uncacheable();
                                 context.builder.inherit_${property.ident}();
                             % endif
                         }
+                        CSSWideKeyword::Revert => unreachable!("Should never get here"),
                     }
                     return;
                 }
diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index fcc6e48b41b..aa2d0247e82 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -452,14 +452,23 @@ impl AnimationValue {
                     % for prop in data.longhands:
                     % if prop.animatable:
                     LonghandId::${prop.camel_case} => {
+                        // FIXME(emilio, bug 1533327): I think
+                        // CSSWideKeyword::Revert handling is not fine here, but
+                        // what to do instead?
+                        //
+                        // Seems we'd need the computed value as if it was
+                        // revert, somehow. Treating it as `unset` seems fine
+                        // for now...
                         let style_struct = match declaration.keyword {
                             % if not prop.style_struct.inherited:
+                            CSSWideKeyword::Revert |
                             CSSWideKeyword::Unset |
                             % endif
                             CSSWideKeyword::Initial => {
                                 initial.get_${prop.style_struct.name_lower}()
                             },
                             % if prop.style_struct.inherited:
+                            CSSWideKeyword::Revert |
                             CSSWideKeyword::Unset |
                             % endif
                             CSSWideKeyword::Inherit => {
@@ -802,29 +811,29 @@ impl ToAnimatedZero for Visibility {
 impl Animate for ClipRect {
     #[inline]
     fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        use crate::values::computed::Length;
-        let animate_component = |this: &Option<Length>, other: &Option<Length>| {
-            match (this.animate(other, procedure)?, procedure) {
-                (None, Procedure::Interpolate { .. }) => Ok(None),
-                (None, _) => Err(()),
-                (result, _) => Ok(result),
+        use crate::values::computed::LengthOrAuto;
+        let animate_component = |this: &LengthOrAuto, other: &LengthOrAuto| {
+            let result = this.animate(other, procedure)?;
+            if let Procedure::Interpolate { .. } = procedure {
+                return Ok(result);
             }
+            if result.is_auto() {
+                // FIXME(emilio): Why? A couple SMIL tests fail without this,
+                // but it seems extremely fishy.
+                return Err(());
+            }
+            Ok(result)
         };
 
         Ok(ClipRect {
-            top:    animate_component(&self.top, &other.top)?,
-            right:  animate_component(&self.right, &other.right)?,
+            top: animate_component(&self.top, &other.top)?,
+            right: animate_component(&self.right, &other.right)?,
             bottom: animate_component(&self.bottom, &other.bottom)?,
-            left:   animate_component(&self.left, &other.left)?,
+            left: animate_component(&self.left, &other.left)?,
         })
     }
 }
 
-impl ToAnimatedZero for ClipRect {
-    #[inline]
-    fn to_animated_zero(&self) -> Result<Self, ()> { Err(()) }
-}
-
 <%
     FILTER_FUNCTIONS = [ 'Blur', 'Brightness', 'Contrast', 'Grayscale',
                          'HueRotate', 'Invert', 'Opacity', 'Saturate',
diff --git a/components/style/properties/longhands/column.mako.rs b/components/style/properties/longhands/column.mako.rs
index 90c37a9710f..f61b78acf46 100644
--- a/components/style/properties/longhands/column.mako.rs
+++ b/components/style/properties/longhands/column.mako.rs
@@ -9,8 +9,8 @@
 ${helpers.predefined_type(
     "column-width",
     "length::NonNegativeLengthOrAuto",
-    "Either::Second(Auto)",
-    initial_specified_value="Either::Second(Auto)",
+    "computed::length::NonNegativeLengthOrAuto::auto()",
+    initial_specified_value="specified::length::NonNegativeLengthOrAuto::auto()",
     extra_prefixes="moz",
     animation_value_type="NonNegativeLengthOrAuto",
     servo_pref="layout.columns.enabled",
diff --git a/components/style/properties/longhands/inherited_svg.mako.rs b/components/style/properties/longhands/inherited_svg.mako.rs
index fcd16833b5f..2bbdc2794c2 100644
--- a/components/style/properties/longhands/inherited_svg.mako.rs
+++ b/components/style/properties/longhands/inherited_svg.mako.rs
@@ -84,7 +84,8 @@ ${helpers.predefined_type(
 )}
 
 ${helpers.predefined_type(
-    "stroke-width", "SVGWidth",
+    "stroke-width",
+    "SVGWidth",
     "computed::SVGWidth::one()",
     products="gecko",
     animation_value_type="crate::values::computed::SVGWidth",
@@ -109,11 +110,11 @@ ${helpers.single_keyword(
 
 ${helpers.predefined_type(
     "stroke-miterlimit",
-    "GreaterThanOrEqualToOneNumber",
+    "NonNegativeNumber",
     "From::from(4.0)",
     products="gecko",
-    animation_value_type="crate::values::computed::GreaterThanOrEqualToOneNumber",
-    spec="https://www.w3.org/TR/SVG11/painting.html#StrokeMiterlimitProperty",
+    animation_value_type="crate::values::computed::NonNegativeNumber",
+    spec="https://www.w3.org/TR/SVG2/painting.html#StrokeMiterlimitProperty",
 )}
 
 ${helpers.predefined_type(
diff --git a/components/style/properties/longhands/inherited_text.mako.rs b/components/style/properties/longhands/inherited_text.mako.rs
index 97d551120a4..f61c8754b5e 100644
--- a/components/style/properties/longhands/inherited_text.mako.rs
+++ b/components/style/properties/longhands/inherited_text.mako.rs
@@ -74,13 +74,13 @@ ${helpers.predefined_type(
     servo_restyle_damage="rebuild_and_reflow",
 )}
 
-// TODO(pcwalton): Support `word-break: keep-all` once we have better CJK support.
-${helpers.single_keyword(
+${helpers.predefined_type(
     "word-break",
-    "normal break-all keep-all",
-    gecko_constant_prefix="NS_STYLE_WORDBREAK",
+    "WordBreak",
+    "computed::WordBreak::Normal",
     animation_value_type="discrete",
     spec="https://drafts.csswg.org/css-text/#propdef-word-break",
+    needs_context=False,
     servo_restyle_damage="rebuild_and_reflow",
 )}
 
@@ -157,7 +157,7 @@ ${helpers.predefined_type(
 ${helpers.predefined_type(
     "word-spacing",
     "WordSpacing",
-    "computed::WordSpacing::normal()",
+    "computed::WordSpacing::zero()",
     animation_value_type="ComputedValue",
     flags="APPLIES_TO_FIRST_LETTER APPLIES_TO_FIRST_LINE APPLIES_TO_PLACEHOLDER",
     spec="https://drafts.csswg.org/css-text/#propdef-word-spacing",
diff --git a/components/style/properties/longhands/padding.mako.rs b/components/style/properties/longhands/padding.mako.rs
index 6c4e2b32cf9..a1262aee0fc 100644
--- a/components/style/properties/longhands/padding.mako.rs
+++ b/components/style/properties/longhands/padding.mako.rs
@@ -39,6 +39,6 @@
         logical=side[1],
         logical_group="scroll-padding",
         spec="https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-padding-%s" % side[0],
-        animation_value_type="ComputedValue",
+        animation_value_type="NonNegativeLengthPercentageOrAuto",
     )}
 % endfor
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index 7e35d318c30..0153d6fe336 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -42,6 +42,7 @@ use crate::values::computed;
 use crate::values::computed::NonNegativeLength;
 use crate::values::serialize_atom_name;
 use crate::rule_tree::StrongRuleNode;
+use crate::Zero;
 use self::computed_value_flags::*;
 use crate::str::{CssString, CssStringBorrow, CssStringWriter};
 
@@ -899,6 +900,8 @@ pub enum CSSWideKeyword {
     Inherit,
     /// The `unset` keyword.
     Unset,
+    /// The `revert` keyword.
+    Revert,
 }
 
 impl CSSWideKeyword {
@@ -907,6 +910,7 @@ impl CSSWideKeyword {
             CSSWideKeyword::Initial => "initial",
             CSSWideKeyword::Inherit => "inherit",
             CSSWideKeyword::Unset => "unset",
+            CSSWideKeyword::Revert => "revert",
         }
     }
 }
@@ -920,6 +924,7 @@ impl CSSWideKeyword {
                 "initial" => CSSWideKeyword::Initial,
                 "inherit" => CSSWideKeyword::Inherit,
                 "unset" => CSSWideKeyword::Unset,
+                "revert" => CSSWideKeyword::Revert,
                 _ => return Err(()),
             }
         };
@@ -2102,6 +2107,7 @@ impl PropertyDeclaration {
     }
 
     /// Returns a CSS-wide keyword if the declaration's value is one.
+    #[inline]
     pub fn get_css_wide_keyword(&self) -> Option<CSSWideKeyword> {
         match *self {
             PropertyDeclaration::CSSWideKeyword(ref declaration) => {
@@ -2585,7 +2591,8 @@ pub mod style_structs {
                     /// Whether the border-${side} property has nonzero width.
                     #[allow(non_snake_case)]
                     pub fn border_${side}_has_nonzero_width(&self) -> bool {
-                        self.border_${side}_width != NonNegativeLength::zero()
+                        use crate::Zero;
+                        !self.border_${side}_width.is_zero()
                     }
                 % endfor
             % elif style_struct.name == "Font":
@@ -2624,7 +2631,8 @@ pub mod style_structs {
                 /// Whether the outline-width property is non-zero.
                 #[inline]
                 pub fn outline_has_nonzero_width(&self) -> bool {
-                    self.outline_width != NonNegativeLength::zero()
+                    use crate::Zero;
+                    !self.outline_width.is_zero()
                 }
             % elif style_struct.name == "Text":
                 /// Whether the text decoration has an underline.
@@ -2718,11 +2726,7 @@ pub mod style_structs {
             /// Whether this is a multicol style.
             #[cfg(feature = "servo")]
             pub fn is_multicol(&self) -> bool {
-                use crate::values::Either;
-                match self.column_width {
-                    Either::First(_width) => true,
-                    Either::Second(_auto) => !self.column_count.is_auto(),
-                }
+                !self.column_width.is_auto() || !self.column_count.is_auto()
             }
         % endif
     }
@@ -3435,22 +3439,16 @@ impl<'a> StyleBuilder<'a> {
     }
 
     % for property in data.longhands:
-    % if property.ident != "font_size":
+    % if not property.style_struct.inherited:
     /// Inherit `${property.ident}` from our parent style.
     #[allow(non_snake_case)]
     pub fn inherit_${property.ident}(&mut self) {
         let inherited_struct =
-        % if property.style_struct.inherited:
-            self.inherited_style.get_${property.style_struct.name_lower}();
-        % else:
             self.inherited_style_ignoring_first_line
                 .get_${property.style_struct.name_lower}();
-        % endif
 
-        % if not property.style_struct.inherited:
-        self.flags.insert(ComputedValueFlags::INHERITS_RESET_STYLE);
         self.modified_reset = true;
-        % endif
+        self.flags.insert(ComputedValueFlags::INHERITS_RESET_STYLE);
 
         % if property.ident == "content":
         self.flags.insert(ComputedValueFlags::INHERITS_CONTENT);
@@ -3472,17 +3470,13 @@ impl<'a> StyleBuilder<'a> {
                 % endif
             );
     }
-
+    % elif property.name != "font-size":
     /// Reset `${property.ident}` to the initial value.
     #[allow(non_snake_case)]
     pub fn reset_${property.ident}(&mut self) {
         let reset_struct =
             self.reset_style.get_${property.style_struct.name_lower}();
 
-        % if not property.style_struct.inherited:
-        self.modified_reset = true;
-        % endif
-
         if self.${property.style_struct.ident}.ptr_eq(reset_struct) {
             return;
         }
@@ -3495,6 +3489,7 @@ impl<'a> StyleBuilder<'a> {
                 % endif
             );
     }
+    % endif
 
     % if not property.is_vector:
     /// Set the `${property.ident}` to the computed value `value`.
@@ -3516,7 +3511,6 @@ impl<'a> StyleBuilder<'a> {
             );
     }
     % endif
-    % endif
     % endfor
     <% del property %>
 
diff --git a/components/style/rule_tree/mod.rs b/components/style/rule_tree/mod.rs
index a2caba6f9f7..f165e1f455f 100644
--- a/components/style/rule_tree/mod.rs
+++ b/components/style/rule_tree/mod.rs
@@ -11,7 +11,7 @@ use crate::applicable_declarations::ApplicableDeclarationList;
 use crate::gecko::selector_parser::PseudoElement;
 use crate::properties::{Importance, LonghandIdSet, PropertyDeclarationBlock};
 use crate::shared_lock::{Locked, SharedRwLockReadGuard, StylesheetGuards};
-use crate::stylesheets::StyleRule;
+use crate::stylesheets::{Origin, StyleRule};
 use crate::thread_state;
 #[cfg(feature = "gecko")]
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
@@ -659,6 +659,25 @@ impl CascadeLevel {
         }
     }
 
+    /// Returns the cascade origin of the rule.
+    #[inline]
+    pub fn origin(&self) -> Origin {
+        match *self {
+            CascadeLevel::UAImportant | CascadeLevel::UANormal => Origin::UserAgent,
+            CascadeLevel::UserImportant | CascadeLevel::UserNormal => Origin::User,
+            CascadeLevel::PresHints |
+            CascadeLevel::InnerShadowNormal |
+            CascadeLevel::SameTreeAuthorNormal |
+            CascadeLevel::StyleAttributeNormal |
+            CascadeLevel::SMILOverride |
+            CascadeLevel::Animations |
+            CascadeLevel::SameTreeAuthorImportant |
+            CascadeLevel::StyleAttributeImportant |
+            CascadeLevel::InnerShadowImportant |
+            CascadeLevel::Transitions => Origin::Author,
+        }
+    }
+
     /// Returns whether this cascade level represents an animation rules.
     #[inline]
     pub fn is_animation(&self) -> bool {
diff --git a/components/style/stylesheets/origin.rs b/components/style/stylesheets/origin.rs
index 69b9b866c86..fc89260abd2 100644
--- a/components/style/stylesheets/origin.rs
+++ b/components/style/stylesheets/origin.rs
@@ -36,6 +36,25 @@ impl Origin {
             _ => return None,
         })
     }
+
+    fn to_index(self) -> i8 {
+        match self {
+            Origin::Author => 0,
+            Origin::User => 1,
+            Origin::UserAgent => 2,
+        }
+    }
+
+    /// Returns an iterator from this origin, towards all the less specific
+    /// origins. So for `UserAgent`, it'd iterate through all origins.
+    #[inline]
+    pub fn following_including(self) -> OriginSetIterator {
+        OriginSetIterator {
+            set: OriginSet::ORIGIN_USER | OriginSet::ORIGIN_AUTHOR | OriginSet::ORIGIN_USER_AGENT,
+            cur: self.to_index(),
+            rev: true,
+        }
+    }
 }
 
 bitflags! {
@@ -57,7 +76,11 @@ impl OriginSet {
     /// See the `OriginSet` documentation for information about the order
     /// origins are iterated.
     pub fn iter(&self) -> OriginSetIterator {
-        OriginSetIterator { set: *self, cur: 0 }
+        OriginSetIterator {
+            set: *self,
+            cur: 0,
+            rev: false,
+        }
     }
 }
 
@@ -79,6 +102,7 @@ impl BitOrAssign<Origin> for OriginSet {
 pub struct OriginSetIterator {
     set: OriginSet,
     cur: i8,
+    rev: bool,
 }
 
 impl Iterator for OriginSetIterator {
@@ -88,7 +112,11 @@ impl Iterator for OriginSetIterator {
         loop {
             let origin = Origin::from_index(self.cur)?;
 
-            self.cur += 1;
+            if self.rev {
+                self.cur -= 1;
+            } else {
+                self.cur += 1;
+            }
 
             if self.set.contains(origin.into()) {
                 return Some(origin);
diff --git a/components/style/traversal.rs b/components/style/traversal.rs
index f1821900bb4..d5a9a5c5033 100644
--- a/components/style/traversal.rs
+++ b/components/style/traversal.rs
@@ -686,7 +686,7 @@ where
             // sibling or cousin. Otherwise, recascading a bunch of identical
             // elements would unnecessarily flood the cache with identical entries.
             //
-            // This is analagous to the obvious "don't insert an element that just
+            // This is analogous to the obvious "don't insert an element that just
             // got a hit in the style sharing cache" behavior in the MatchAndCascade
             // handling above.
             //
diff --git a/components/style/values/animated/mod.rs b/components/style/values/animated/mod.rs
index 6bc7f624e34..3b83c71e6e2 100644
--- a/components/style/values/animated/mod.rs
+++ b/components/style/values/animated/mod.rs
@@ -16,7 +16,7 @@ use crate::values::computed::Image;
 use crate::values::specified::SVGPathData;
 use crate::values::CSSFloat;
 use app_units::Au;
-use euclid::{Point2D, Size2D};
+use euclid::Point2D;
 use smallvec::SmallVec;
 use std::cmp;
 
@@ -241,19 +241,6 @@ impl Animate for Au {
     }
 }
 
-impl<T> Animate for Size2D<T>
-where
-    T: Animate,
-{
-    #[inline]
-    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        Ok(Size2D::new(
-            self.width.animate(&other.width, procedure)?,
-            self.height.animate(&other.height, procedure)?,
-        ))
-    }
-}
-
 impl<T> Animate for Point2D<T>
 where
     T: Animate,
@@ -397,16 +384,13 @@ where
     }
 }
 
-impl<T> ToAnimatedZero for Size2D<T>
+impl<T> ToAnimatedZero for Vec<T>
 where
     T: ToAnimatedZero,
 {
     #[inline]
     fn to_animated_zero(&self) -> Result<Self, ()> {
-        Ok(Size2D::new(
-            self.width.to_animated_zero()?,
-            self.height.to_animated_zero()?,
-        ))
+        self.iter().map(|v| v.to_animated_zero()).collect()
     }
 }
 
diff --git a/components/style/values/animated/svg.rs b/components/style/values/animated/svg.rs
index 4564b787c6d..436bb73d658 100644
--- a/components/style/values/animated/svg.rs
+++ b/components/style/values/animated/svg.rs
@@ -8,10 +8,8 @@ use super::{Animate, Procedure, ToAnimatedZero};
 use crate::properties::animated_properties::ListAnimation;
 use crate::values::animated::color::Color as AnimatedColor;
 use crate::values::computed::url::ComputedUrl;
-use crate::values::computed::{LengthPercentage, Number, NumberOrPercentage};
 use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
-use crate::values::generics::svg::{SVGLength, SVGPaint, SvgLengthPercentageOrNumber};
-use crate::values::generics::svg::{SVGOpacity, SVGStrokeDashArray};
+use crate::values::generics::svg::{SVGPaint, SVGStrokeDashArray};
 
 /// Animated SVGPaint.
 pub type IntermediateSVGPaint = SVGPaint<AnimatedColor, ComputedUrl>;
@@ -26,67 +24,6 @@ impl ToAnimatedZero for IntermediateSVGPaint {
     }
 }
 
-// FIXME: We need to handle calc here properly, see
-// https://bugzilla.mozilla.org/show_bug.cgi?id=1386967
-fn to_number_or_percentage(
-    value: &SvgLengthPercentageOrNumber<LengthPercentage, Number>,
-) -> Result<NumberOrPercentage, ()> {
-    Ok(match *value {
-        SvgLengthPercentageOrNumber::LengthPercentage(ref l) => match l.specified_percentage() {
-            Some(p) => {
-                if l.unclamped_length().px() != 0. {
-                    return Err(());
-                }
-                NumberOrPercentage::Percentage(p)
-            },
-            None => NumberOrPercentage::Number(l.length().px()),
-        },
-        SvgLengthPercentageOrNumber::Number(ref n) => NumberOrPercentage::Number(*n),
-    })
-}
-
-impl Animate for SvgLengthPercentageOrNumber<LengthPercentage, Number> {
-    #[inline]
-    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        let this = to_number_or_percentage(self)?;
-        let other = to_number_or_percentage(other)?;
-
-        match (this, other) {
-            (NumberOrPercentage::Number(ref this), NumberOrPercentage::Number(ref other)) => Ok(
-                SvgLengthPercentageOrNumber::Number(this.animate(other, procedure)?),
-            ),
-            (
-                NumberOrPercentage::Percentage(ref this),
-                NumberOrPercentage::Percentage(ref other),
-            ) => Ok(SvgLengthPercentageOrNumber::LengthPercentage(
-                LengthPercentage::new_percent(this.animate(other, procedure)?),
-            )),
-            _ => Err(()),
-        }
-    }
-}
-
-impl ComputeSquaredDistance for SvgLengthPercentageOrNumber<LengthPercentage, Number> {
-    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
-        to_number_or_percentage(self)?.compute_squared_distance(&to_number_or_percentage(other)?)
-    }
-}
-
-impl<L> Animate for SVGLength<L>
-where
-    L: Animate + Clone,
-{
-    #[inline]
-    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        match (self, other) {
-            (&SVGLength::Length(ref this), &SVGLength::Length(ref other)) => {
-                Ok(SVGLength::Length(this.animate(other, procedure)?))
-            },
-            _ => Err(()),
-        }
-    }
-}
-
 /// <https://www.w3.org/TR/SVG11/painting.html#StrokeDasharrayProperty>
 impl<L> Animate for SVGStrokeDashArray<L>
 where
@@ -121,36 +58,3 @@ where
         }
     }
 }
-
-impl<L> ToAnimatedZero for SVGStrokeDashArray<L>
-where
-    L: ToAnimatedZero,
-{
-    #[inline]
-    fn to_animated_zero(&self) -> Result<Self, ()> {
-        match *self {
-            SVGStrokeDashArray::Values(ref values) => Ok(SVGStrokeDashArray::Values(
-                values
-                    .iter()
-                    .map(ToAnimatedZero::to_animated_zero)
-                    .collect::<Result<Vec<_>, _>>()?,
-            )),
-            SVGStrokeDashArray::ContextValue => Ok(SVGStrokeDashArray::ContextValue),
-        }
-    }
-}
-
-impl<O> Animate for SVGOpacity<O>
-where
-    O: Animate + Clone,
-{
-    #[inline]
-    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        match (self, other) {
-            (&SVGOpacity::Opacity(ref this), &SVGOpacity::Opacity(ref other)) => {
-                Ok(SVGOpacity::Opacity(this.animate(other, procedure)?))
-            },
-            _ => Err(()),
-        }
-    }
-}
diff --git a/components/style/values/animated/transform.rs b/components/style/values/animated/transform.rs
index c341ca770ed..0c322d8fccc 100644
--- a/components/style/values/animated/transform.rs
+++ b/components/style/values/animated/transform.rs
@@ -22,7 +22,7 @@ use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
 use crate::values::generics::transform::{self, Transform, TransformOperation};
 use crate::values::generics::transform::{Rotate, Scale, Translate};
 use crate::values::CSSFloat;
-use num_traits::Zero;
+use crate::Zero;
 use std::cmp;
 
 // ------------------------------------
@@ -1003,18 +1003,12 @@ impl Animate for ComputedTransformOperation {
             (&TransformOperation::Matrix(ref this), &TransformOperation::Matrix(ref other)) => {
                 Ok(TransformOperation::Matrix(this.animate(other, procedure)?))
             },
-            (&TransformOperation::Skew(ref fx, None), &TransformOperation::Skew(ref tx, None)) => {
-                Ok(TransformOperation::Skew(fx.animate(tx, procedure)?, None))
-            },
             (
                 &TransformOperation::Skew(ref fx, ref fy),
                 &TransformOperation::Skew(ref tx, ref ty),
             ) => Ok(TransformOperation::Skew(
                 fx.animate(tx, procedure)?,
-                Some(
-                    fy.unwrap_or(Angle::zero())
-                        .animate(&ty.unwrap_or(Angle::zero()), procedure)?,
-                ),
+                fy.animate(ty, procedure)?,
             )),
             (&TransformOperation::SkewX(ref f), &TransformOperation::SkewX(ref t)) => {
                 Ok(TransformOperation::SkewX(f.animate(t, procedure)?))
@@ -1031,21 +1025,11 @@ impl Animate for ComputedTransformOperation {
                 fz.animate(tz, procedure)?,
             )),
             (
-                &TransformOperation::Translate(ref fx, None),
-                &TransformOperation::Translate(ref tx, None),
-            ) => Ok(TransformOperation::Translate(
-                fx.animate(tx, procedure)?,
-                None,
-            )),
-            (
                 &TransformOperation::Translate(ref fx, ref fy),
                 &TransformOperation::Translate(ref tx, ref ty),
             ) => Ok(TransformOperation::Translate(
                 fx.animate(tx, procedure)?,
-                Some(
-                    fy.unwrap_or(LengthPercentage::zero())
-                        .animate(&ty.unwrap_or(LengthPercentage::zero()), procedure)?,
-                ),
+                fy.animate(ty, procedure)?,
             )),
             (&TransformOperation::TranslateX(ref f), &TransformOperation::TranslateX(ref t)) => {
                 Ok(TransformOperation::TranslateX(f.animate(t, procedure)?))
@@ -1073,22 +1057,12 @@ impl Animate for ComputedTransformOperation {
             (&TransformOperation::ScaleZ(ref f), &TransformOperation::ScaleZ(ref t)) => Ok(
                 TransformOperation::ScaleZ(animate_multiplicative_factor(*f, *t, procedure)?),
             ),
-            (&TransformOperation::Scale(ref f, None), &TransformOperation::Scale(ref t, None)) => {
-                Ok(TransformOperation::Scale(
-                    animate_multiplicative_factor(*f, *t, procedure)?,
-                    None,
-                ))
-            },
             (
                 &TransformOperation::Scale(ref fx, ref fy),
                 &TransformOperation::Scale(ref tx, ref ty),
             ) => Ok(TransformOperation::Scale(
                 animate_multiplicative_factor(*fx, *tx, procedure)?,
-                Some(animate_multiplicative_factor(
-                    fy.unwrap_or(*fx),
-                    ty.unwrap_or(*tx),
-                    procedure,
-                )?),
+                animate_multiplicative_factor(*fy, *ty, procedure)?,
             )),
             (
                 &TransformOperation::Rotate3D(fx, fy, fz, fa),
diff --git a/components/style/values/computed/angle.rs b/components/style/values/computed/angle.rs
index d30f02d7200..76e44575dfb 100644
--- a/components/style/values/computed/angle.rs
+++ b/components/style/values/computed/angle.rs
@@ -6,7 +6,7 @@
 
 use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
 use crate::values::CSSFloat;
-use num_traits::Zero;
+use crate::Zero;
 use std::f64::consts::PI;
 use std::fmt::{self, Write};
 use std::{f32, f64};
diff --git a/components/style/values/computed/border.rs b/components/style/values/computed/border.rs
index e85b5a3e5d6..62c8e3883f6 100644
--- a/components/style/values/computed/border.rs
+++ b/components/style/values/computed/border.rs
@@ -12,8 +12,9 @@ use crate::values::generics::border::BorderImageSlice as GenericBorderImageSlice
 use crate::values::generics::border::BorderRadius as GenericBorderRadius;
 use crate::values::generics::border::BorderSpacing as GenericBorderSpacing;
 use crate::values::generics::rect::Rect;
-use crate::values::generics::size::Size;
+use crate::values::generics::size::Size2D;
 use crate::values::generics::NonNegative;
+use crate::Zero;
 use app_units::Au;
 
 pub use crate::values::specified::border::BorderImageRepeat;
@@ -59,7 +60,7 @@ impl BorderImageSlice {
 impl BorderSpacing {
     /// Returns `0 0`.
     pub fn zero() -> Self {
-        GenericBorderSpacing(Size::new(
+        GenericBorderSpacing(Size2D::new(
             NonNegativeLength::zero(),
             NonNegativeLength::zero(),
         ))
@@ -75,29 +76,3 @@ impl BorderSpacing {
         Au::from(*self.0.height())
     }
 }
-
-impl BorderCornerRadius {
-    /// Returns `0 0`.
-    pub fn zero() -> Self {
-        GenericBorderCornerRadius(Size::new(
-            NonNegativeLengthPercentage::zero(),
-            NonNegativeLengthPercentage::zero(),
-        ))
-    }
-}
-
-impl BorderRadius {
-    /// Returns whether all the values are `0px`.
-    pub fn all_zero(&self) -> bool {
-        fn all(corner: &BorderCornerRadius) -> bool {
-            fn is_zero(l: &NonNegativeLengthPercentage) -> bool {
-                *l == NonNegativeLengthPercentage::zero()
-            }
-            is_zero(corner.0.width()) && is_zero(corner.0.height())
-        }
-        all(&self.top_left) &&
-            all(&self.top_right) &&
-            all(&self.bottom_left) &&
-            all(&self.bottom_right)
-    }
-}
diff --git a/components/style/values/computed/length.rs b/components/style/values/computed/length.rs
index f578bbbd5ce..1262e4dd1d5 100644
--- a/components/style/values/computed/length.rs
+++ b/components/style/values/computed/length.rs
@@ -12,11 +12,11 @@ use crate::values::generics::length as generics;
 use crate::values::generics::length::{
     GenericLengthOrNumber, MaxSize as GenericMaxSize, Size as GenericSize,
 };
-use crate::values::generics::transform::IsZeroLength;
 use crate::values::generics::NonNegative;
 use crate::values::specified::length::ViewportPercentageLength;
 use crate::values::specified::length::{AbsoluteLength, FontBaseSize, FontRelativeLength};
-use crate::values::{specified, Auto, CSSFloat, Either, Normal};
+use crate::values::{specified, CSSFloat, Either, Normal};
+use crate::Zero;
 use app_units::Au;
 use ordered_float::NotNan;
 use std::fmt::{self, Write};
@@ -203,12 +203,7 @@ impl LengthPercentage {
             return None;
         }
 
-        if self.clamping_mode.clamp(self.percentage.0) != self.percentage.0 {
-            debug_assert!(self.was_calc);
-            return None;
-        }
-
-        Some(self.percentage)
+        Some(Percentage(self.clamping_mode.clamp(self.percentage.0)))
     }
 
     /// Convert the computed value into used value.
@@ -347,12 +342,6 @@ impl ToComputedValue for specified::CalcLengthPercentage {
 }
 
 impl LengthPercentage {
-    #[inline]
-    #[allow(missing_docs)]
-    pub fn zero() -> LengthPercentage {
-        LengthPercentage::new(Length::new(0.), None)
-    }
-
     /// 1px length value for SVG defaults
     #[inline]
     pub fn one() -> LengthPercentage {
@@ -433,14 +422,13 @@ impl ToComputedValue for specified::LengthPercentage {
     }
 
     fn from_computed_value(computed: &LengthPercentage) -> Self {
-        let length = computed.unclamped_length();
         if let Some(p) = computed.as_percentage() {
             return specified::LengthPercentage::Percentage(p);
         }
 
-        if !computed.has_percentage && computed.clamping_mode.clamp(length.px()) == length.px() {
+        if !computed.has_percentage {
             return specified::LengthPercentage::Length(ToComputedValue::from_computed_value(
-                &length,
+                &computed.length(),
             ));
         }
 
@@ -448,9 +436,13 @@ impl ToComputedValue for specified::LengthPercentage {
     }
 }
 
-impl IsZeroLength for LengthPercentage {
+impl Zero for LengthPercentage {
+    fn zero() -> Self {
+        LengthPercentage::new(Length::zero(), None)
+    }
+
     #[inline]
-    fn is_zero_length(&self) -> bool {
+    fn is_zero(&self) -> bool {
         self.is_definitely_zero()
     }
 }
@@ -459,12 +451,6 @@ impl IsZeroLength for LengthPercentage {
 /// length-percentage or auto.
 macro_rules! computed_length_percentage_or_auto {
     ($inner:ty) => {
-        /// Returns the `0` value.
-        #[inline]
-        pub fn zero() -> Self {
-            generics::LengthPercentageOrAuto::LengthPercentage(<$inner>::zero())
-        }
-
         /// Returns the used value.
         #[inline]
         pub fn to_used_value(&self, percentage_basis: Au) -> Option<Au> {
@@ -553,12 +539,6 @@ impl From<Au> for LengthPercentage {
 }
 
 impl NonNegativeLengthPercentage {
-    /// Get zero value.
-    #[inline]
-    pub fn zero() -> Self {
-        NonNegative(LengthPercentage::zero())
-    }
-
     /// Returns true if the computed value is absolute 0 or 0%.
     #[inline]
     pub fn is_definitely_zero(&self) -> bool {
@@ -662,12 +642,16 @@ impl CSSPixelLength {
     pub fn clamp_to_non_negative(self) -> Self {
         CSSPixelLength::new(self.0.max(0.))
     }
+}
 
-    /// Zero value
-    #[inline]
-    pub fn zero() -> Self {
+impl Zero for CSSPixelLength {
+    fn zero() -> Self {
         CSSPixelLength::new(0.)
     }
+
+    fn is_zero(&self) -> bool {
+        self.px() == 0.
+    }
 }
 
 impl ToCss for CSSPixelLength {
@@ -717,7 +701,10 @@ impl From<Au> for CSSPixelLength {
 pub type Length = CSSPixelLength;
 
 /// Either a computed `<length>` or the `auto` keyword.
-pub type LengthOrAuto = Either<Length, Auto>;
+pub type LengthOrAuto = generics::GenericLengthPercentageOrAuto<Length>;
+
+/// Either a non-negative `<length>` or the `auto` keyword.
+pub type NonNegativeLengthOrAuto = generics::GenericLengthPercentageOrAuto<NonNegativeLength>;
 
 /// Either a computed `<length>` or a `<number>` value.
 pub type LengthOrNumber = GenericLengthOrNumber<Length, Number>;
@@ -749,12 +736,6 @@ impl NonNegativeLength {
         NonNegative(Length::new(px.max(0.)))
     }
 
-    /// Return a zero value.
-    #[inline]
-    pub fn zero() -> Self {
-        Self::new(0.)
-    }
-
     /// Return the pixel value of |NonNegativeLength|.
     #[inline]
     pub fn px(&self) -> CSSFloat {
@@ -801,9 +782,6 @@ impl From<NonNegativeLength> for Au {
     }
 }
 
-/// Either a computed NonNegativeLength or the `auto` keyword.
-pub type NonNegativeLengthOrAuto = Either<NonNegativeLength, Auto>;
-
 /// Either a computed NonNegativeLength or the `normal` keyword.
 pub type NonNegativeLengthOrNormal = Either<NonNegativeLength, Normal>;
 
diff --git a/components/style/values/computed/mod.rs b/components/style/values/computed/mod.rs
index 6fe36d684f2..1f7d1e3eddc 100644
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@@ -10,7 +10,7 @@ use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent
 use super::generics::grid::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
 use super::generics::grid::{TrackList as GenericTrackList, TrackSize as GenericTrackSize};
 use super::generics::transform::IsParallelTo;
-use super::generics::{GreaterThanOrEqualToOne, NonNegative};
+use super::generics::{self, GreaterThanOrEqualToOne, NonNegative};
 use super::specified;
 use super::{CSSFloat, CSSInteger};
 use crate::context::QuirksMode;
@@ -27,8 +27,6 @@ use euclid::Size2D;
 use std::cell::RefCell;
 use std::cmp;
 use std::f32;
-use std::fmt::{self, Write};
-use style_traits::{CssWriter, ToCss};
 
 #[cfg(feature = "gecko")]
 pub use self::align::{AlignContent, AlignItems, JustifyContent, JustifyItems, SelfAlignment};
@@ -62,7 +60,7 @@ pub use self::gecko::ScrollSnapPoint;
 pub use self::image::{Gradient, GradientItem, Image, ImageLayer, LineDirection, MozImageRect};
 pub use self::length::{CSSPixelLength, ExtremumLength, NonNegativeLength};
 pub use self::length::{Length, LengthOrNumber, LengthPercentage, NonNegativeLengthOrNumber};
-pub use self::length::{LengthPercentageOrAuto, MaxSize, Size};
+pub use self::length::{LengthOrAuto, LengthPercentageOrAuto, MaxSize, Size};
 pub use self::length::{NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto};
 #[cfg(feature = "gecko")]
 pub use self::list::ListStyleType;
@@ -78,7 +76,7 @@ pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
 pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::table::XSpan;
 pub use self::text::{InitialLetter, LetterSpacing, LineHeight};
-pub use self::text::{OverflowWrap, TextOverflow, WordSpacing};
+pub use self::text::{OverflowWrap, TextOverflow, WordBreak, WordSpacing};
 pub use self::text::{TextAlign, TextEmphasisPosition, TextEmphasisStyle};
 pub use self::time::Time;
 pub use self::transform::{Rotate, Scale, Transform, TransformOperation};
@@ -637,52 +635,8 @@ impl From<CSSInteger> for PositiveInteger {
     }
 }
 
-#[allow(missing_docs)]
-#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
-#[derive(Clone, ComputeSquaredDistance, Copy, Debug, PartialEq)]
-/// A computed cliprect for clip and image-region
-pub struct ClipRect {
-    pub top: Option<Length>,
-    pub right: Option<Length>,
-    pub bottom: Option<Length>,
-    pub left: Option<Length>,
-}
-
-impl ToCss for ClipRect {
-    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
-    where
-        W: Write,
-    {
-        dest.write_str("rect(")?;
-        if let Some(top) = self.top {
-            top.to_css(dest)?;
-            dest.write_str(", ")?;
-        } else {
-            dest.write_str("auto, ")?;
-        }
-
-        if let Some(right) = self.right {
-            right.to_css(dest)?;
-            dest.write_str(", ")?;
-        } else {
-            dest.write_str("auto, ")?;
-        }
-
-        if let Some(bottom) = self.bottom {
-            bottom.to_css(dest)?;
-            dest.write_str(", ")?;
-        } else {
-            dest.write_str("auto, ")?;
-        }
-
-        if let Some(left) = self.left {
-            left.to_css(dest)?;
-        } else {
-            dest.write_str("auto")?;
-        }
-        dest.write_str(")")
-    }
-}
+/// rect(...)
+pub type ClipRect = generics::ClipRect<LengthOrAuto>;
 
 /// rect(...) | auto
 pub type ClipRectOrAuto = Either<ClipRect, Auto>;
diff --git a/components/style/values/computed/percentage.rs b/components/style/values/computed/percentage.rs
index 67bdda76033..4f39a7a7274 100644
--- a/components/style/values/computed/percentage.rs
+++ b/components/style/values/computed/percentage.rs
@@ -7,6 +7,7 @@
 use crate::values::animated::ToAnimatedValue;
 use crate::values::generics::NonNegative;
 use crate::values::{serialize_percentage, CSSFloat};
+use crate::Zero;
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
 
@@ -31,12 +32,6 @@ use style_traits::{CssWriter, ToCss};
 pub struct Percentage(pub CSSFloat);
 
 impl Percentage {
-    /// 0%
-    #[inline]
-    pub fn zero() -> Self {
-        Percentage(0.)
-    }
-
     /// 100%
     #[inline]
     pub fn hundred() -> Self {
@@ -56,6 +51,16 @@ impl Percentage {
     }
 }
 
+impl Zero for Percentage {
+    fn zero() -> Self {
+        Percentage(0.)
+    }
+
+    fn is_zero(&self) -> bool {
+        self.0 == 0.
+    }
+}
+
 impl ToCss for Percentage {
     fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
     where
@@ -69,12 +74,6 @@ impl ToCss for Percentage {
 pub type NonNegativePercentage = NonNegative<Percentage>;
 
 impl NonNegativePercentage {
-    /// 0%
-    #[inline]
-    pub fn zero() -> Self {
-        NonNegative(Percentage::zero())
-    }
-
     /// 100%
     #[inline]
     pub fn hundred() -> Self {
diff --git a/components/style/values/computed/position.rs b/components/style/values/computed/position.rs
index d6f9161903b..f0f8fe198a6 100644
--- a/components/style/values/computed/position.rs
+++ b/components/style/values/computed/position.rs
@@ -11,6 +11,7 @@ use crate::values::computed::{Integer, LengthPercentage, Percentage};
 use crate::values::generics::position::Position as GenericPosition;
 use crate::values::generics::position::ZIndex as GenericZIndex;
 pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas};
+use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 
diff --git a/components/style/values/computed/svg.rs b/components/style/values/computed/svg.rs
index f3ca86aa5b0..f05e9f836da 100644
--- a/components/style/values/computed/svg.rs
+++ b/components/style/values/computed/svg.rs
@@ -6,10 +6,10 @@
 
 use crate::values::computed::color::Color;
 use crate::values::computed::url::ComputedUrl;
-use crate::values::computed::{LengthPercentage, NonNegativeLengthPercentage};
-use crate::values::computed::{NonNegativeNumber, Number, Opacity};
+use crate::values::computed::{LengthPercentage, NonNegativeLengthPercentage, Opacity};
 use crate::values::generics::svg as generic;
 use crate::values::RGBA;
+use crate::Zero;
 
 pub use crate::values::specified::SVGPaintOrder;
 
@@ -40,58 +40,29 @@ impl SVGPaint {
     }
 }
 
-/// A value of <length> | <percentage> | <number> for stroke-dashoffset.
-/// <https://www.w3.org/TR/SVG11/painting.html#StrokeProperties>
-pub type SvgLengthPercentageOrNumber =
-    generic::SvgLengthPercentageOrNumber<LengthPercentage, Number>;
-
 /// <length> | <percentage> | <number> | context-value
-pub type SVGLength = generic::SVGLength<SvgLengthPercentageOrNumber>;
+pub type SVGLength = generic::SVGLength<LengthPercentage>;
 
 impl SVGLength {
     /// `0px`
     pub fn zero() -> Self {
-        generic::SVGLength::Length(generic::SvgLengthPercentageOrNumber::LengthPercentage(
-            LengthPercentage::zero(),
-        ))
-    }
-}
-
-/// A value of <length> | <percentage> | <number> for stroke-width/stroke-dasharray.
-/// <https://www.w3.org/TR/SVG11/painting.html#StrokeProperties>
-pub type NonNegativeSvgLengthPercentageOrNumber =
-    generic::SvgLengthPercentageOrNumber<NonNegativeLengthPercentage, NonNegativeNumber>;
-
-// FIXME(emilio): This is really hacky, and can go away with a bit of work on
-// the clone_stroke_width code in gecko.mako.rs.
-impl Into<NonNegativeSvgLengthPercentageOrNumber> for SvgLengthPercentageOrNumber {
-    fn into(self) -> NonNegativeSvgLengthPercentageOrNumber {
-        match self {
-            generic::SvgLengthPercentageOrNumber::LengthPercentage(lop) => {
-                generic::SvgLengthPercentageOrNumber::LengthPercentage(lop.into())
-            },
-            generic::SvgLengthPercentageOrNumber::Number(num) => {
-                generic::SvgLengthPercentageOrNumber::Number(num.into())
-            },
-        }
+        generic::SVGLength::LengthPercentage(LengthPercentage::zero())
     }
 }
 
 /// An non-negative wrapper of SVGLength.
-pub type SVGWidth = generic::SVGLength<NonNegativeSvgLengthPercentageOrNumber>;
+pub type SVGWidth = generic::SVGLength<NonNegativeLengthPercentage>;
 
 impl SVGWidth {
     /// `1px`.
     pub fn one() -> Self {
         use crate::values::generics::NonNegative;
-        generic::SVGLength::Length(generic::SvgLengthPercentageOrNumber::LengthPercentage(
-            NonNegative(LengthPercentage::one()),
-        ))
+        generic::SVGLength::LengthPercentage(NonNegative(LengthPercentage::one()))
     }
 }
 
 /// [ <length> | <percentage> | <number> ]# | context-value
-pub type SVGStrokeDashArray = generic::SVGStrokeDashArray<NonNegativeSvgLengthPercentageOrNumber>;
+pub type SVGStrokeDashArray = generic::SVGStrokeDashArray<NonNegativeLengthPercentage>;
 
 impl Default for SVGStrokeDashArray {
     fn default() -> Self {
diff --git a/components/style/values/computed/text.rs b/components/style/values/computed/text.rs
index 2c9a9593ecc..911891bf33b 100644
--- a/components/style/values/computed/text.rs
+++ b/components/style/values/computed/text.rs
@@ -7,28 +7,97 @@
 #[cfg(feature = "servo")]
 use crate::properties::StyleBuilder;
 use crate::values::computed::length::{Length, LengthPercentage};
-use crate::values::computed::{NonNegativeLength, NonNegativeNumber};
+use crate::values::computed::{Context, NonNegativeLength, NonNegativeNumber, ToComputedValue};
 use crate::values::generics::text::InitialLetter as GenericInitialLetter;
 use crate::values::generics::text::LineHeight as GenericLineHeight;
 use crate::values::generics::text::Spacing;
-use crate::values::specified::text::TextOverflowSide;
+use crate::values::specified::text::{self as specified, TextOverflowSide};
 use crate::values::specified::text::{TextEmphasisFillMode, TextEmphasisShapeKeyword};
 use crate::values::{CSSFloat, CSSInteger};
+use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 
-pub use crate::values::specified::OverflowWrap;
 pub use crate::values::specified::TextAlignKeyword as TextAlign;
 pub use crate::values::specified::TextEmphasisPosition;
+pub use crate::values::specified::{OverflowWrap, WordBreak};
 
 /// A computed value for the `initial-letter` property.
 pub type InitialLetter = GenericInitialLetter<CSSFloat, CSSInteger>;
 
 /// A computed value for the `letter-spacing` property.
-pub type LetterSpacing = Spacing<Length>;
+#[repr(transparent)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedValue,
+    ToAnimatedZero,
+)]
+pub struct LetterSpacing(pub Length);
+
+impl LetterSpacing {
+    /// Return the `normal` computed value, which is just zero.
+    #[inline]
+    pub fn normal() -> Self {
+        LetterSpacing(Length::zero())
+    }
+}
+
+impl ToCss for LetterSpacing {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        // https://drafts.csswg.org/css-text/#propdef-letter-spacing
+        //
+        // For legacy reasons, a computed letter-spacing of zero yields a
+        // resolved value (getComputedStyle() return value) of normal.
+        if self.0.is_zero() {
+            return dest.write_str("normal");
+        }
+        self.0.to_css(dest)
+    }
+}
+
+impl ToComputedValue for specified::LetterSpacing {
+    type ComputedValue = LetterSpacing;
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            Spacing::Normal => LetterSpacing(Length::zero()),
+            Spacing::Value(ref v) => LetterSpacing(v.to_computed_value(context)),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        if computed.0.is_zero() {
+            return Spacing::Normal;
+        }
+        Spacing::Value(ToComputedValue::from_computed_value(&computed.0))
+    }
+}
 
 /// A computed value for the `word-spacing` property.
-pub type WordSpacing = Spacing<LengthPercentage>;
+pub type WordSpacing = LengthPercentage;
+
+impl ToComputedValue for specified::WordSpacing {
+    type ComputedValue = WordSpacing;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            Spacing::Normal => LengthPercentage::zero(),
+            Spacing::Value(ref v) => v.to_computed_value(context),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Spacing::Value(ToComputedValue::from_computed_value(computed))
+    }
+}
 
 /// A computed value for the `line-height` property.
 pub type LineHeight = GenericLineHeight<NonNegativeNumber, NonNegativeLength>;
diff --git a/components/style/values/computed/transform.rs b/components/style/values/computed/transform.rs
index dd3fe20754c..e23ec1524ff 100644
--- a/components/style/values/computed/transform.rs
+++ b/components/style/values/computed/transform.rs
@@ -9,8 +9,8 @@ use crate::values::animated::transform::{Perspective, Scale3D, Translate3D};
 use crate::values::animated::ToAnimatedZero;
 use crate::values::computed::{Angle, Integer, Length, LengthPercentage, Number, Percentage};
 use crate::values::generics::transform as generic;
+use crate::Zero;
 use euclid::{Transform3D, Vector3D};
-use num_traits::Zero;
 
 pub use crate::values::generics::transform::TransformStyle;
 
@@ -371,15 +371,14 @@ impl TransformOperation {
     pub fn to_translate_3d(&self) -> Self {
         match *self {
             generic::TransformOperation::Translate3D(..) => self.clone(),
-            generic::TransformOperation::TranslateX(ref x) |
-            generic::TransformOperation::Translate(ref x, None) => {
+            generic::TransformOperation::TranslateX(ref x) => {
                 generic::TransformOperation::Translate3D(
                     x.clone(),
                     LengthPercentage::zero(),
                     Length::zero(),
                 )
             },
-            generic::TransformOperation::Translate(ref x, Some(ref y)) => {
+            generic::TransformOperation::Translate(ref x, ref y) => {
                 generic::TransformOperation::Translate3D(x.clone(), y.clone(), Length::zero())
             },
             generic::TransformOperation::TranslateY(ref y) => {
@@ -426,10 +425,7 @@ impl TransformOperation {
     pub fn to_scale_3d(&self) -> Self {
         match *self {
             generic::TransformOperation::Scale3D(..) => self.clone(),
-            generic::TransformOperation::Scale(s, None) => {
-                generic::TransformOperation::Scale3D(s, s, 1.)
-            },
-            generic::TransformOperation::Scale(x, Some(y)) => {
+            generic::TransformOperation::Scale(x, y) => {
                 generic::TransformOperation::Scale3D(x, y, 1.)
             },
             generic::TransformOperation::ScaleX(x) => {
@@ -494,7 +490,7 @@ impl ToAnimatedZero for TransformOperation {
                 Ok(generic::TransformOperation::Scale3D(1.0, 1.0, 1.0))
             },
             generic::TransformOperation::Scale(_, _) => {
-                Ok(generic::TransformOperation::Scale(1.0, Some(1.0)))
+                Ok(generic::TransformOperation::Scale(1.0, 1.0))
             },
             generic::TransformOperation::ScaleX(..) => Ok(generic::TransformOperation::ScaleX(1.0)),
             generic::TransformOperation::ScaleY(..) => Ok(generic::TransformOperation::ScaleY(1.0)),
@@ -585,7 +581,7 @@ impl Translate {
         match *self {
             generic::Translate::None => None,
             generic::Translate::Translate(tx, ty) => {
-                Some(generic::TransformOperation::Translate(tx, Some(ty)))
+                Some(generic::TransformOperation::Translate(tx, ty))
             },
             generic::Translate::Translate3D(tx, ty, tz) => {
                 Some(generic::TransformOperation::Translate3D(tx, ty, tz))
@@ -596,9 +592,7 @@ impl Translate {
     /// Convert Translate to TransformOperation.
     pub fn from_transform_operation(operation: &TransformOperation) -> Translate {
         match *operation {
-            generic::TransformOperation::Translate(tx, Some(ty)) => {
-                generic::Translate::Translate(tx, ty)
-            },
+            generic::TransformOperation::Translate(tx, ty) => generic::Translate::Translate(tx, ty),
             generic::TransformOperation::Translate3D(tx, ty, tz) => {
                 generic::Translate::Translate3D(tx, ty, tz)
             },
@@ -615,7 +609,7 @@ impl Scale {
     pub fn to_transform_operation(&self) -> Option<TransformOperation> {
         match *self {
             generic::Scale::None => None,
-            generic::Scale::Scale(sx, sy) => Some(generic::TransformOperation::Scale(sx, Some(sy))),
+            generic::Scale::Scale(sx, sy) => Some(generic::TransformOperation::Scale(sx, sy)),
             generic::Scale::Scale3D(sx, sy, sz) => {
                 Some(generic::TransformOperation::Scale3D(sx, sy, sz))
             },
@@ -625,8 +619,7 @@ impl Scale {
     /// Convert Scale to TransformOperation.
     pub fn from_transform_operation(operation: &TransformOperation) -> Scale {
         match *operation {
-            generic::TransformOperation::Scale(sx, Some(sy)) => generic::Scale::Scale(sx, sy),
-            generic::TransformOperation::Scale(sx, None) => generic::Scale::Scale(sx, sx),
+            generic::TransformOperation::Scale(sx, sy) => generic::Scale::Scale(sx, sy),
             generic::TransformOperation::Scale3D(sx, sy, sz) => generic::Scale::Scale3D(sx, sy, sz),
             _ => unreachable!("Found unexpected value for scale"),
         }
diff --git a/components/style/values/generics/background.rs b/components/style/values/generics/background.rs
index 14ac9744b14..3780f9a4fc3 100644
--- a/components/style/values/generics/background.rs
+++ b/components/style/values/generics/background.rs
@@ -5,8 +5,13 @@
 //! Generic types for CSS values related to backgrounds.
 
 use crate::values::generics::length::{GenericLengthPercentageOrAuto, LengthPercentageOrAuto};
-use std::fmt::{self, Write};
-use style_traits::{CssWriter, ToCss};
+
+fn width_and_height_are_auto<L>(
+    width: &LengthPercentageOrAuto<L>,
+    height: &LengthPercentageOrAuto<L>,
+) -> bool {
+    width.is_auto() && height.is_auto()
+}
 
 /// A generic value for the `background-size` property.
 #[derive(
@@ -21,6 +26,7 @@ use style_traits::{CssWriter, ToCss};
     ToAnimatedValue,
     ToAnimatedZero,
     ToComputedValue,
+    ToCss,
 )]
 #[repr(C, u8)]
 pub enum GenericBackgroundSize<LengthPercent> {
@@ -29,6 +35,10 @@ pub enum GenericBackgroundSize<LengthPercent> {
         /// Explicit width.
         width: GenericLengthPercentageOrAuto<LengthPercent>,
         /// Explicit height.
+        /// NOTE(emilio): We should probably simplify all these in case `width`
+        /// and `height` are the same, but all other browsers agree on only
+        /// special-casing `auto`.
+        #[css(contextual_skip_if = "width_and_height_are_auto")]
         height: GenericLengthPercentageOrAuto<LengthPercent>,
     },
     /// `cover`
@@ -41,32 +51,6 @@ pub enum GenericBackgroundSize<LengthPercent> {
 
 pub use self::GenericBackgroundSize as BackgroundSize;
 
-impl<LengthPercentage> ToCss for BackgroundSize<LengthPercentage>
-where
-    LengthPercentage: ToCss,
-{
-    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
-    where
-        W: Write,
-    {
-        match self {
-            BackgroundSize::ExplicitSize { width, height } => {
-                width.to_css(dest)?;
-                // NOTE(emilio): We should probably simplify all these in case
-                // `width == `height`, but all other browsers agree on only
-                // special-casing `auto`.
-                if !width.is_auto() || !height.is_auto() {
-                    dest.write_str(" ")?;
-                    height.to_css(dest)?;
-                }
-                Ok(())
-            },
-            BackgroundSize::Cover => dest.write_str("cover"),
-            BackgroundSize::Contain => dest.write_str("contain"),
-        }
-    }
-}
-
 impl<LengthPercentage> BackgroundSize<LengthPercentage> {
     /// Returns `auto auto`.
     pub fn auto() -> Self {
diff --git a/components/style/values/generics/basic_shape.rs b/components/style/values/generics/basic_shape.rs
index f224f936ccb..975fbdb797d 100644
--- a/components/style/values/generics/basic_shape.rs
+++ b/components/style/values/generics/basic_shape.rs
@@ -11,6 +11,7 @@ use crate::values::generics::border::BorderRadius;
 use crate::values::generics::position::Position;
 use crate::values::generics::rect::Rect;
 use crate::values::specified::SVGPathData;
+use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 
@@ -127,7 +128,7 @@ pub enum BasicShape<H, V, LengthPercentage, NonNegativeLengthPercentage> {
 )]
 pub struct InsetRect<LengthPercentage, NonNegativeLengthPercentage> {
     pub rect: Rect<LengthPercentage>,
-    pub round: Option<BorderRadius<NonNegativeLengthPercentage>>,
+    pub round: BorderRadius<NonNegativeLengthPercentage>,
 }
 
 /// <https://drafts.csswg.org/css-shapes/#funcdef-circle>
@@ -311,7 +312,7 @@ impl<B, T, U> ToAnimatedZero for ShapeSource<B, T, U> {
 impl<Length, NonNegativeLength> ToCss for InsetRect<Length, NonNegativeLength>
 where
     Length: ToCss + PartialEq,
-    NonNegativeLength: ToCss + PartialEq,
+    NonNegativeLength: ToCss + PartialEq + Zero,
 {
     fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
     where
@@ -319,9 +320,9 @@ where
     {
         dest.write_str("inset(")?;
         self.rect.to_css(dest)?;
-        if let Some(ref radius) = self.round {
+        if !self.round.is_zero() {
             dest.write_str(" round ")?;
-            radius.to_css(dest)?;
+            self.round.to_css(dest)?;
         }
         dest.write_str(")")
     }
diff --git a/components/style/values/generics/border.rs b/components/style/values/generics/border.rs
index ffd30e98678..df6427e888f 100644
--- a/components/style/values/generics/border.rs
+++ b/components/style/values/generics/border.rs
@@ -5,7 +5,8 @@
 //! Generic types for CSS values related to borders.
 
 use crate::values::generics::rect::Rect;
-use crate::values::generics::size::Size;
+use crate::values::generics::size::Size2D;
+use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 
@@ -53,12 +54,25 @@ pub use self::GenericBorderImageSlice as BorderImageSlice;
     ToComputedValue,
     ToCss,
 )]
-pub struct BorderCornerRadius<L>(#[css(field_bound)] pub Size<L>);
+#[repr(C)]
+pub struct GenericBorderCornerRadius<L>(#[css(field_bound)] pub Size2D<L>);
+
+pub use self::GenericBorderCornerRadius as BorderCornerRadius;
 
 impl<L> BorderCornerRadius<L> {
     /// Trivially create a `BorderCornerRadius`.
     pub fn new(w: L, h: L) -> Self {
-        BorderCornerRadius(Size::new(w, h))
+        BorderCornerRadius(Size2D::new(w, h))
+    }
+}
+
+impl<L: Zero> Zero for BorderCornerRadius<L> {
+    fn zero() -> Self {
+        BorderCornerRadius(Size2D::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        self.0.is_zero()
     }
 }
 
@@ -77,12 +91,13 @@ impl<L> BorderCornerRadius<L> {
     ToComputedValue,
     ToCss,
 )]
-pub struct BorderSpacing<L>(#[css(field_bound)] pub Size<L>);
+#[repr(transparent)]
+pub struct BorderSpacing<L>(#[css(field_bound)] pub Size2D<L>);
 
 impl<L> BorderSpacing<L> {
     /// Trivially create a `BorderCornerRadius`.
     pub fn new(w: L, h: L) -> Self {
-        BorderSpacing(Size::new(w, h))
+        BorderSpacing(Size2D::new(w, h))
     }
 }
 
@@ -101,17 +116,20 @@ impl<L> BorderSpacing<L> {
     ToAnimatedValue,
     ToComputedValue,
 )]
-pub struct BorderRadius<LengthPercentage> {
+#[repr(C)]
+pub struct GenericBorderRadius<LengthPercentage> {
     /// The top left radius.
-    pub top_left: BorderCornerRadius<LengthPercentage>,
+    pub top_left: GenericBorderCornerRadius<LengthPercentage>,
     /// The top right radius.
-    pub top_right: BorderCornerRadius<LengthPercentage>,
+    pub top_right: GenericBorderCornerRadius<LengthPercentage>,
     /// The bottom right radius.
-    pub bottom_right: BorderCornerRadius<LengthPercentage>,
+    pub bottom_right: GenericBorderCornerRadius<LengthPercentage>,
     /// The bottom left radius.
-    pub bottom_left: BorderCornerRadius<LengthPercentage>,
+    pub bottom_left: GenericBorderCornerRadius<LengthPercentage>,
 }
 
+pub use self::GenericBorderRadius as BorderRadius;
+
 impl<L> BorderRadius<L> {
     /// Returns a new `BorderRadius<L>`.
     #[inline]
@@ -128,12 +146,7 @@ impl<L> BorderRadius<L> {
             bottom_left: bl,
         }
     }
-}
 
-impl<L> BorderRadius<L>
-where
-    L: PartialEq + ToCss,
-{
     /// Serialises two given rects following the syntax of the `border-radius``
     /// property.
     pub fn serialize_rects<W>(
@@ -142,14 +155,11 @@ where
         dest: &mut CssWriter<W>,
     ) -> fmt::Result
     where
+        L: PartialEq + ToCss,
         W: Write,
     {
         widths.to_css(dest)?;
-        if widths.0 != heights.0 ||
-            widths.1 != heights.1 ||
-            widths.2 != heights.2 ||
-            widths.3 != heights.3
-        {
+        if widths != heights {
             dest.write_str(" / ")?;
             heights.to_css(dest)?;
         }
@@ -157,6 +167,24 @@ where
     }
 }
 
+impl<L: Zero> Zero for BorderRadius<L> {
+    fn zero() -> Self {
+        Self::new(
+            BorderCornerRadius::<L>::zero(),
+            BorderCornerRadius::<L>::zero(),
+            BorderCornerRadius::<L>::zero(),
+            BorderCornerRadius::<L>::zero(),
+        )
+    }
+
+    fn is_zero(&self) -> bool {
+        self.top_left.is_zero() &&
+            self.top_right.is_zero() &&
+            self.bottom_right.is_zero() &&
+            self.bottom_left.is_zero()
+    }
+}
+
 impl<L> ToCss for BorderRadius<L>
 where
     L: PartialEq + ToCss,
@@ -172,8 +200,8 @@ where
             bottom_left: BorderCornerRadius(ref bl),
         } = *self;
 
-        let widths = Rect::new(&tl.0.width, &tr.0.width, &br.0.width, &bl.0.width);
-        let heights = Rect::new(&tl.0.height, &tr.0.height, &br.0.height, &bl.0.height);
+        let widths = Rect::new(&tl.width, &tr.width, &br.width, &bl.width);
+        let heights = Rect::new(&tl.height, &tr.height, &br.height, &bl.height);
 
         Self::serialize_rects(widths, heights, dest)
     }
diff --git a/components/style/values/generics/length.rs b/components/style/values/generics/length.rs
index 1a83f58054c..076a02a4a0f 100644
--- a/components/style/values/generics/length.rs
+++ b/components/style/values/generics/length.rs
@@ -7,8 +7,8 @@
 use crate::parser::{Parse, ParserContext};
 #[cfg(feature = "gecko")]
 use crate::values::computed::ExtremumLength;
+use crate::Zero;
 use cssparser::Parser;
-use num_traits::Zero;
 use style_traits::ParseError;
 
 /// A `<length-percentage> | auto` value.
@@ -67,6 +67,19 @@ impl<LengthPercentage> LengthPercentageOrAuto<LengthPercentage> {
     }
 }
 
+impl<LengthPercentage: Zero> Zero for LengthPercentageOrAuto<LengthPercentage> {
+    fn zero() -> Self {
+        LengthPercentageOrAuto::LengthPercentage(Zero::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            LengthPercentageOrAuto::LengthPercentage(ref l) => l.is_zero(),
+            LengthPercentageOrAuto::Auto => false,
+        }
+    }
+}
+
 impl<LengthPercentage: Parse> Parse for LengthPercentageOrAuto<LengthPercentage> {
     fn parse<'i, 't>(
         context: &ParserContext,
@@ -186,12 +199,15 @@ pub enum GenericLengthOrNumber<L, N> {
 
 pub use self::GenericLengthOrNumber as LengthOrNumber;
 
-impl<L, N> LengthOrNumber<L, N> {
-    /// Returns `0`.
-    pub fn zero() -> Self
-    where
-        N: Zero,
-    {
-        LengthOrNumber::Number(num_traits::Zero::zero())
+impl<L, N: Zero> Zero for LengthOrNumber<L, N> {
+    fn zero() -> Self {
+        LengthOrNumber::Number(Zero::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            LengthOrNumber::Number(ref n) => n.is_zero(),
+            LengthOrNumber::Length(..) => false,
+        }
     }
 }
diff --git a/components/style/values/generics/mod.rs b/components/style/values/generics/mod.rs
index 737c88e7ba7..e054db7281f 100644
--- a/components/style/values/generics/mod.rs
+++ b/components/style/values/generics/mod.rs
@@ -8,8 +8,8 @@
 use super::CustomIdent;
 use crate::counter_style::{parse_counter_style_name, Symbols};
 use crate::parser::{Parse, ParserContext};
+use crate::Zero;
 use cssparser::Parser;
-use num_traits::Zero;
 use std::ops::Add;
 use style_traits::{KeywordsCollectFn, ParseError};
 use style_traits::{SpecifiedValueInfo, StyleParseErrorKind};
@@ -212,3 +212,26 @@ impl<T: Zero> Zero for NonNegative<T> {
     ToCss,
 )]
 pub struct GreaterThanOrEqualToOne<T>(pub T);
+
+/// A clip rect for clip and image-region
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+)]
+#[css(function = "rect", comma)]
+pub struct ClipRect<LengthOrAuto> {
+    pub top: LengthOrAuto,
+    pub right: LengthOrAuto,
+    pub bottom: LengthOrAuto,
+    pub left: LengthOrAuto,
+}
diff --git a/components/style/values/generics/size.rs b/components/style/values/generics/size.rs
index a5a5c86eac6..96e0003128f 100644
--- a/components/style/values/generics/size.rs
+++ b/components/style/values/generics/size.rs
@@ -5,11 +5,10 @@
 //! Generic type for CSS properties that are composed by two dimensions.
 
 use crate::parser::ParserContext;
-use crate::values::animated::ToAnimatedValue;
+use crate::Zero;
 use cssparser::Parser;
-use euclid::Size2D;
 use std::fmt::{self, Write};
-use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, ToCss};
+use style_traits::{CssWriter, ParseError, ToCss};
 
 /// A generic size, for `border-*-radius` longhand properties, or
 /// `border-spacing`.
@@ -21,29 +20,36 @@ use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, ToCss};
     Debug,
     MallocSizeOf,
     PartialEq,
+    SpecifiedValueInfo,
     ToAnimatedZero,
+    ToAnimatedValue,
     ToComputedValue,
 )]
-pub struct Size<L>(pub Size2D<L>);
+#[allow(missing_docs)]
+#[repr(C)]
+pub struct Size2D<L> {
+    pub width: L,
+    pub height: L,
+}
 
-impl<L> Size<L> {
+impl<L> Size2D<L> {
     #[inline]
-    /// Create a new `Size` for an area of given width and height.
-    pub fn new(width: L, height: L) -> Size<L> {
-        Size(Size2D::new(width, height))
+    /// Create a new `Size2D` for an area of given width and height.
+    pub fn new(width: L, height: L) -> Self {
+        Self { width, height }
     }
 
     /// Returns the width component.
     pub fn width(&self) -> &L {
-        &self.0.width
+        &self.width
     }
 
     /// Returns the height component.
     pub fn height(&self) -> &L {
-        &self.0.height
+        &self.height
     }
 
-    /// Parse a `Size` with a given parsing function.
+    /// Parse a `Size2D` with a given parsing function.
     pub fn parse_with<'i, 't, F>(
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
@@ -61,7 +67,7 @@ impl<L> Size<L> {
     }
 }
 
-impl<L> ToCss for Size<L>
+impl<L> ToCss for Size2D<L>
 where
     L: ToCss + PartialEq,
 {
@@ -69,40 +75,23 @@ where
     where
         W: Write,
     {
-        self.0.width.to_css(dest)?;
+        self.width.to_css(dest)?;
 
-        if self.0.height != self.0.width {
+        if self.height != self.width {
             dest.write_str(" ")?;
-            self.0.height.to_css(dest)?;
+            self.height.to_css(dest)?;
         }
 
         Ok(())
     }
 }
 
-impl<L> ToAnimatedValue for Size<L>
-where
-    L: ToAnimatedValue,
-{
-    type AnimatedValue = Size<L::AnimatedValue>;
-
-    #[inline]
-    fn to_animated_value(self) -> Self::AnimatedValue {
-        Size(Size2D::new(
-            self.0.width.to_animated_value(),
-            self.0.height.to_animated_value(),
-        ))
+impl<L: Zero> Zero for Size2D<L> {
+    fn zero() -> Self {
+        Self::new(L::zero(), L::zero())
     }
 
-    #[inline]
-    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
-        Size(Size2D::new(
-            L::from_animated_value(animated.0.width),
-            L::from_animated_value(animated.0.height),
-        ))
+    fn is_zero(&self) -> bool {
+        self.width.is_zero() && self.height.is_zero()
     }
 }
-
-impl<L: SpecifiedValueInfo> SpecifiedValueInfo for Size<L> {
-    const SUPPORTED_TYPES: u8 = L::SUPPORTED_TYPES;
-}
diff --git a/components/style/values/generics/svg.rs b/components/style/values/generics/svg.rs
index 7f52126a748..6a4d2411e76 100644
--- a/components/style/values/generics/svg.rs
+++ b/components/style/values/generics/svg.rs
@@ -128,64 +128,26 @@ impl<ColorType: Parse, UrlPaintServer: Parse> Parse for SVGPaint<ColorType, UrlP
     }
 }
 
-/// A value of <length> | <percentage> | <number> for svg which allow unitless length.
-/// <https://www.w3.org/TR/SVG11/painting.html#StrokeProperties>
-#[derive(
-    Clone,
-    Copy,
-    Debug,
-    MallocSizeOf,
-    PartialEq,
-    Parse,
-    SpecifiedValueInfo,
-    ToAnimatedValue,
-    ToAnimatedZero,
-    ToComputedValue,
-    ToCss,
-)]
-pub enum SvgLengthPercentageOrNumber<LengthPercentage, Number> {
-    /// <number>
-    ///
-    /// Note that this needs to be before, so it gets parsed before the length,
-    /// to handle `0` correctly as a number instead of a `<length>`.
-    Number(Number),
-    /// <length> | <percentage>
-    LengthPercentage(LengthPercentage),
-}
-
-/// Whether the `context-value` value is enabled.
-#[cfg(feature = "gecko")]
-pub fn is_context_value_enabled(_: &ParserContext) -> bool {
-    use crate::gecko_bindings::structs::mozilla;
-    unsafe { mozilla::StaticPrefs_sVarCache_gfx_font_rendering_opentype_svg_enabled }
-}
-
-/// Whether the `context-value` value is enabled.
-#[cfg(not(feature = "gecko"))]
-pub fn is_context_value_enabled(_: &ParserContext) -> bool {
-    false
-}
-
 /// An SVG length value supports `context-value` in addition to length.
 #[derive(
+    Animate,
     Clone,
     ComputeSquaredDistance,
     Copy,
     Debug,
     MallocSizeOf,
     PartialEq,
-    Parse,
     SpecifiedValueInfo,
     ToAnimatedValue,
     ToAnimatedZero,
     ToComputedValue,
     ToCss,
 )]
-pub enum SVGLength<LengthType> {
+pub enum SVGLength<L> {
     /// `<length> | <percentage> | <number>`
-    Length(LengthType),
+    LengthPercentage(L),
     /// `context-value`
-    #[parse(condition = "is_context_value_enabled")]
+    #[animation(error)]
     ContextValue,
 }
 
@@ -197,13 +159,14 @@ pub enum SVGLength<LengthType> {
     PartialEq,
     SpecifiedValueInfo,
     ToAnimatedValue,
+    ToAnimatedZero,
     ToComputedValue,
     ToCss,
 )]
-pub enum SVGStrokeDashArray<LengthType> {
+pub enum SVGStrokeDashArray<L> {
     /// `[ <length> | <percentage> | <number> ]#`
     #[css(comma)]
-    Values(#[css(if_empty = "none", iterable)] Vec<LengthType>),
+    Values(#[css(if_empty = "none", iterable)] Vec<L>),
     /// `context-value`
     ContextValue,
 }
@@ -211,6 +174,7 @@ pub enum SVGStrokeDashArray<LengthType> {
 /// An SVG opacity value accepts `context-{fill,stroke}-opacity` in
 /// addition to opacity value.
 #[derive(
+    Animate,
     Clone,
     ComputeSquaredDistance,
     Copy,
@@ -227,7 +191,9 @@ pub enum SVGOpacity<OpacityType> {
     /// `<opacity-value>`
     Opacity(OpacityType),
     /// `context-fill-opacity`
+    #[animation(error)]
     ContextFillOpacity,
     /// `context-stroke-opacity`
+    #[animation(error)]
     ContextStrokeOpacity,
 }
diff --git a/components/style/values/generics/text.rs b/components/style/values/generics/text.rs
index 029c5681318..7dae932faac 100644
--- a/components/style/values/generics/text.rs
+++ b/components/style/values/generics/text.rs
@@ -5,9 +5,7 @@
 //! Generic types for text properties.
 
 use crate::parser::ParserContext;
-use crate::values::animated::{Animate, Procedure, ToAnimatedZero};
-use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
-use app_units::Au;
+use crate::values::animated::ToAnimatedZero;
 use cssparser::Parser;
 use style_traits::ParseError;
 
@@ -31,9 +29,7 @@ impl<N, I> InitialLetter<N, I> {
 }
 
 /// A generic spacing value for the `letter-spacing` and `word-spacing` properties.
-#[derive(
-    Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue, ToCss,
-)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
 pub enum Spacing<Value> {
     /// `normal`
     Normal,
@@ -63,51 +59,6 @@ impl<Value> Spacing<Value> {
         }
         parse(context, input).map(Spacing::Value)
     }
-
-    /// Returns the spacing value, if not `normal`.
-    #[inline]
-    pub fn value(&self) -> Option<&Value> {
-        match *self {
-            Spacing::Normal => None,
-            Spacing::Value(ref value) => Some(value),
-        }
-    }
-}
-
-impl<Value> Animate for Spacing<Value>
-where
-    Value: Animate + From<Au>,
-{
-    #[inline]
-    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
-        if let (&Spacing::Normal, &Spacing::Normal) = (self, other) {
-            return Ok(Spacing::Normal);
-        }
-        let zero = Value::from(Au(0));
-        let this = self.value().unwrap_or(&zero);
-        let other = other.value().unwrap_or(&zero);
-        Ok(Spacing::Value(this.animate(other, procedure)?))
-    }
-}
-
-impl<V> ComputeSquaredDistance for Spacing<V>
-where
-    V: ComputeSquaredDistance + From<Au>,
-{
-    #[inline]
-    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
-        let zero = V::from(Au(0));
-        let this = self.value().unwrap_or(&zero);
-        let other = other.value().unwrap_or(&zero);
-        this.compute_squared_distance(other)
-    }
-}
-
-impl<V> ToAnimatedZero for Spacing<V> {
-    #[inline]
-    fn to_animated_zero(&self) -> Result<Self, ()> {
-        Err(())
-    }
 }
 
 /// A generic value for the `line-height` property.
@@ -123,18 +74,21 @@ impl<V> ToAnimatedZero for Spacing<V> {
     ToAnimatedValue,
     ToCss,
 )]
-pub enum LineHeight<Number, LengthPercentage> {
+#[repr(C, u8)]
+pub enum GenericLineHeight<N, L> {
     /// `normal`
     Normal,
     /// `-moz-block-height`
     #[cfg(feature = "gecko")]
     MozBlockHeight,
     /// `<number>`
-    Number(Number),
-    /// `<length-or-percentage>`
-    Length(LengthPercentage),
+    Number(N),
+    /// `<length-percentage>`
+    Length(L),
 }
 
+pub use self::GenericLineHeight as LineHeight;
+
 impl<N, L> ToAnimatedZero for LineHeight<N, L> {
     #[inline]
     fn to_animated_zero(&self) -> Result<Self, ()> {
diff --git a/components/style/values/generics/transform.rs b/components/style/values/generics/transform.rs
index 6c60e76cbf6..3e091162b2e 100644
--- a/components/style/values/generics/transform.rs
+++ b/components/style/values/generics/transform.rs
@@ -10,9 +10,9 @@ use crate::values::specified::angle::Angle as SpecifiedAngle;
 use crate::values::specified::length::Length as SpecifiedLength;
 use crate::values::specified::length::LengthPercentage as SpecifiedLengthPercentage;
 use crate::values::{computed, CSSFloat};
+use crate::Zero;
 use app_units::Au;
 use euclid::{self, Rect, Transform3D};
-use num_traits::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 
@@ -106,9 +106,18 @@ impl<H, V, D> TransformOrigin<H, V, D> {
     }
 }
 
+fn is_same<N: PartialEq>(x: &N, y: &N) -> bool {
+    x == y
+}
+
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue, ToCss)]
 /// A single operation in the list of a `transform` value
-pub enum TransformOperation<Angle, Number, Length, Integer, LengthPercentage> {
+pub enum TransformOperation<Angle, Number, Length, Integer, LengthPercentage>
+where
+    Angle: Zero,
+    LengthPercentage: Zero,
+    Number: PartialEq,
+{
     /// Represents a 2D 2x3 matrix.
     Matrix(Matrix<Number>),
     /// Represents a 3D 4x4 matrix.
@@ -119,7 +128,7 @@ pub enum TransformOperation<Angle, Number, Length, Integer, LengthPercentage> {
     ///
     /// Syntax can be skew(angle) or skew(angle, angle)
     #[css(comma, function)]
-    Skew(Angle, Option<Angle>),
+    Skew(Angle, #[css(skip_if = "Zero::is_zero")] Angle),
     /// skewX(angle)
     #[css(function = "skewX")]
     SkewX(Angle),
@@ -128,7 +137,10 @@ pub enum TransformOperation<Angle, Number, Length, Integer, LengthPercentage> {
     SkewY(Angle),
     /// translate(x, y) or translate(x)
     #[css(comma, function)]
-    Translate(LengthPercentage, Option<LengthPercentage>),
+    Translate(
+        LengthPercentage,
+        #[css(skip_if = "Zero::is_zero")] LengthPercentage,
+    ),
     /// translateX(x)
     #[css(function = "translateX")]
     TranslateX(LengthPercentage),
@@ -143,14 +155,9 @@ pub enum TransformOperation<Angle, Number, Length, Integer, LengthPercentage> {
     Translate3D(LengthPercentage, LengthPercentage, Length),
     /// A 2D scaling factor.
     ///
-    /// `scale(2)` is parsed as `Scale(Number::new(2.0), None)` and is equivalent to
-    /// writing `scale(2, 2)` (`Scale(Number::new(2.0), Some(Number::new(2.0)))`).
-    ///
-    /// Negative values are allowed and flip the element.
-    ///
     /// Syntax can be scale(factor) or scale(factor, factor)
     #[css(comma, function)]
-    Scale(Number, Option<Number>),
+    Scale(Number, #[css(contextual_skip_if = "is_same")] Number),
     /// scaleX(factor)
     #[css(function = "scaleX")]
     ScaleX(Number),
@@ -214,6 +221,10 @@ pub struct Transform<T>(#[css(if_empty = "none", iterable)] pub Vec<T>);
 
 impl<Angle, Number, Length, Integer, LengthPercentage>
     TransformOperation<Angle, Number, Length, Integer, LengthPercentage>
+where
+    Angle: Zero,
+    LengthPercentage: Zero,
+    Number: PartialEq,
 {
     /// Check if it is any rotate function.
     pub fn is_rotate(&self) -> bool {
@@ -333,10 +344,10 @@ impl ToRadians for SpecifiedAngle {
 impl<Angle, Number, Length, Integer, LoP> ToMatrix
     for TransformOperation<Angle, Number, Length, Integer, LoP>
 where
-    Angle: ToRadians + Copy,
-    Number: Copy + Into<f32> + Into<f64>,
+    Angle: Zero + ToRadians + Copy,
+    Number: PartialEq + Copy + Into<f32> + Into<f64>,
     Length: ToAbsoluteLength,
-    LoP: ToAbsoluteLength,
+    LoP: Zero + ToAbsoluteLength,
 {
     #[inline]
     fn is_3d(&self) -> bool {
@@ -389,7 +400,7 @@ where
                 m.cast()
             },
             Scale3D(sx, sy, sz) => Transform3D::create_scale(sx.into(), sy.into(), sz.into()),
-            Scale(sx, sy) => Transform3D::create_scale(sx.into(), sy.unwrap_or(sx).into(), 1.),
+            Scale(sx, sy) => Transform3D::create_scale(sx.into(), sy.into(), 1.),
             ScaleX(s) => Transform3D::create_scale(s.into(), 1., 1.),
             ScaleY(s) => Transform3D::create_scale(1., s.into(), 1.),
             ScaleZ(s) => Transform3D::create_scale(1., 1., s.into()),
@@ -398,12 +409,12 @@ where
                 let ty = ty.to_pixel_length(reference_height)? as f64;
                 Transform3D::create_translation(tx, ty, tz.to_pixel_length(None)? as f64)
             },
-            Translate(ref tx, Some(ref ty)) => {
+            Translate(ref tx, ref ty) => {
                 let tx = tx.to_pixel_length(reference_width)? as f64;
                 let ty = ty.to_pixel_length(reference_height)? as f64;
                 Transform3D::create_translation(tx, ty, 0.)
             },
-            TranslateX(ref t) | Translate(ref t, None) => {
+            TranslateX(ref t) => {
                 let t = t.to_pixel_length(reference_width)? as f64;
                 Transform3D::create_translation(t, 0., 0.)
             },
@@ -416,7 +427,7 @@ where
             },
             Skew(theta_x, theta_y) => Transform3D::create_skew(
                 euclid::Angle::radians(theta_x.radians64()),
-                euclid::Angle::radians(theta_y.map_or(0., |a| a.radians64())),
+                euclid::Angle::radians(theta_y.radians64()),
             ),
             SkewX(theta) => Transform3D::create_skew(
                 euclid::Angle::radians(theta.radians64()),
@@ -629,64 +640,44 @@ impl<Number: ToCss + PartialEq> ToCss for Scale<Number> {
 }
 
 #[derive(
-    Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToAnimatedZero, ToComputedValue,
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
 )]
-/// A value of the `Translate` property
+/// A value of the `translate` property
+///
+/// https://drafts.csswg.org/css-transforms-2/#individual-transform-serialization:
+///
+/// If a 2d translation is specified, the property must serialize with only one
+/// or two values (per usual, if the second value is 0px, the default, it must
+/// be omitted when serializing).
+///
+/// If a 3d translation is specified, all three values must be serialized.
+///
+/// We don't omit the 3rd component even if it is 0px for now, and the
+/// related spec issue is https://github.com/w3c/csswg-drafts/issues/3305
 ///
 /// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
-pub enum Translate<LengthPercentage, Length> {
+pub enum Translate<LengthPercentage, Length>
+where
+    LengthPercentage: Zero,
+{
     /// 'none'
     None,
     /// '<length-percentage>' or '<length-percentage> <length-percentage>'
-    Translate(LengthPercentage, LengthPercentage),
+    Translate(
+        LengthPercentage,
+        #[css(skip_if = "Zero::is_zero")] LengthPercentage,
+    ),
     /// '<length-percentage> <length-percentage> <length>'
     Translate3D(LengthPercentage, LengthPercentage, Length),
 }
 
-/// A trait to check if this is a zero length.
-/// An alternative way is use num_traits::Zero. However, in order to implement num_traits::Zero,
-/// we also have to implement Add, which may be complicated for LengthPercentage::Calc.
-/// We could do this if other types also need it. If so, we could drop this trait.
-pub trait IsZeroLength {
-    /// Returns true if this is a zero length.
-    fn is_zero_length(&self) -> bool;
-}
-
-impl<LoP: ToCss + IsZeroLength, L: ToCss> ToCss for Translate<LoP, L> {
-    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
-    where
-        W: fmt::Write,
-    {
-        // The spec says:
-        // 1. If a 2d translation is specified, the property must serialize with only one or two
-        //    values (per usual, if the second value is 0px, the default, it must be omitted when
-        //    serializing).
-        // 2. If a 3d translation is specified, all three values must be serialized.
-        // https://drafts.csswg.org/css-transforms-2/#individual-transform-serialization
-        //
-        // We don't omit the 3rd component even if it is 0px for now, and the related
-        // spec issue is https://github.com/w3c/csswg-drafts/issues/3305
-        match *self {
-            Translate::None => dest.write_str("none"),
-            Translate::Translate(ref x, ref y) => {
-                x.to_css(dest)?;
-                if !y.is_zero_length() {
-                    dest.write_char(' ')?;
-                    y.to_css(dest)?;
-                }
-                Ok(())
-            },
-            Translate::Translate3D(ref x, ref y, ref z) => {
-                x.to_css(dest)?;
-                dest.write_char(' ')?;
-                y.to_css(dest)?;
-                dest.write_char(' ')?;
-                z.to_css(dest)
-            },
-        }
-    }
-}
-
 #[allow(missing_docs)]
 #[derive(
     Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToComputedValue, ToCss,
diff --git a/components/style/values/mod.rs b/components/style/values/mod.rs
index ccda0f290c1..e29b8923af7 100644
--- a/components/style/values/mod.rs
+++ b/components/style/values/mod.rs
@@ -160,7 +160,7 @@ impl CustomIdent {
         excluding: &[&str],
     ) -> Result<Self, ParseError<'i>> {
         let valid = match_ignore_ascii_case! { ident,
-            "initial" | "inherit" | "unset" | "default" => false,
+            "initial" | "inherit" | "unset" | "default" | "revert" => false,
             _ => true
         };
         if !valid {
diff --git a/components/style/values/specified/angle.rs b/components/style/values/specified/angle.rs
index 35a0944aed5..01eb58368b9 100644
--- a/components/style/values/specified/angle.rs
+++ b/components/style/values/specified/angle.rs
@@ -9,6 +9,7 @@ use crate::values::computed::angle::Angle as ComputedAngle;
 use crate::values::computed::{Context, ToComputedValue};
 use crate::values::specified::calc::CalcNode;
 use crate::values::CSSFloat;
+use crate::Zero;
 use cssparser::{Parser, Token};
 use std::f32::consts::PI;
 use std::fmt::{self, Write};
@@ -32,6 +33,21 @@ pub enum AngleDimension {
     Turn(CSSFloat),
 }
 
+impl Zero for AngleDimension {
+    fn zero() -> Self {
+        AngleDimension::Deg(0.)
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            AngleDimension::Deg(ref f) |
+            AngleDimension::Grad(ref f) |
+            AngleDimension::Rad(ref f) |
+            AngleDimension::Turn(ref f) => *f == 0.,
+        }
+    }
+}
+
 impl AngleDimension {
     /// Returns the amount of degrees this angle represents.
     #[inline]
@@ -58,6 +74,19 @@ pub struct Angle {
     was_calc: bool,
 }
 
+impl Zero for Angle {
+    fn zero() -> Self {
+        Self {
+            value: Zero::zero(),
+            was_calc: false,
+        }
+    }
+
+    fn is_zero(&self) -> bool {
+        self.value.is_zero()
+    }
+}
+
 impl ToCss for Angle {
     fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
     where
@@ -101,6 +130,11 @@ impl Angle {
         }
     }
 
+    /// Return `0deg`.
+    pub fn zero() -> Self {
+        Self::from_degrees(0.0, false)
+    }
+
     /// Returns the value of the angle in degrees, mostly for `calc()`.
     #[inline]
     pub fn degrees(&self) -> CSSFloat {
@@ -113,12 +147,6 @@ impl Angle {
         self.was_calc
     }
 
-    /// Returns `0deg`.
-    #[inline]
-    pub fn zero() -> Self {
-        Self::from_degrees(0.0, false)
-    }
-
     /// Returns an `Angle` parsed from a `calc()` expression.
     pub fn from_calc(degrees: CSSFloat) -> Self {
         Angle {
diff --git a/components/style/values/specified/basic_shape.rs b/components/style/values/specified/basic_shape.rs
index b757c8eec48..014ce439d3c 100644
--- a/components/style/values/specified/basic_shape.rs
+++ b/components/style/values/specified/basic_shape.rs
@@ -18,6 +18,7 @@ use crate::values::specified::position::{HorizontalPosition, Position, VerticalP
 use crate::values::specified::url::SpecifiedUrl;
 use crate::values::specified::SVGPathData;
 use crate::values::specified::{LengthPercentage, NonNegativeLengthPercentage};
+use crate::Zero;
 use cssparser::Parser;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
@@ -202,9 +203,9 @@ impl InsetRect {
     ) -> Result<Self, ParseError<'i>> {
         let rect = Rect::parse_with(context, input, LengthPercentage::parse)?;
         let round = if input.try(|i| i.expect_ident_matching("round")).is_ok() {
-            Some(BorderRadius::parse(context, input)?)
+            BorderRadius::parse(context, input)?
         } else {
-            None
+            BorderRadius::zero()
         };
         Ok(generic::InsetRect { rect, round })
     }
diff --git a/components/style/values/specified/border.rs b/components/style/values/specified/border.rs
index e16d37b4786..d0ef8126482 100644
--- a/components/style/values/specified/border.rs
+++ b/components/style/values/specified/border.rs
@@ -12,9 +12,10 @@ use crate::values::generics::border::BorderImageSlice as GenericBorderImageSlice
 use crate::values::generics::border::BorderRadius as GenericBorderRadius;
 use crate::values::generics::border::BorderSpacing as GenericBorderSpacing;
 use crate::values::generics::rect::Rect;
-use crate::values::generics::size::Size;
+use crate::values::generics::size::Size2D;
 use crate::values::specified::length::{NonNegativeLength, NonNegativeLengthPercentage};
 use crate::values::specified::{AllowQuirks, NonNegativeNumber, NonNegativeNumberOrPercentage};
+use crate::Zero;
 use cssparser::Parser;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ParseError, ToCss};
@@ -228,7 +229,7 @@ impl Parse for BorderCornerRadius {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        Size::parse_with(context, input, NonNegativeLengthPercentage::parse)
+        Size2D::parse_with(context, input, NonNegativeLengthPercentage::parse)
             .map(GenericBorderCornerRadius)
     }
 }
@@ -238,7 +239,7 @@ impl Parse for BorderSpacing {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        Size::parse_with(context, input, |context, input| {
+        Size2D::parse_with(context, input, |context, input| {
             NonNegativeLength::parse_quirky(context, input, AllowQuirks::Yes).map(From::from)
         })
         .map(GenericBorderSpacing)
diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index 2495cca3d6c..d4b66e42ab9 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -752,25 +752,23 @@ pub fn assert_touch_action_matches() {
 
 bitflags! {
     #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue)]
-    #[value_info(other_values = "none,strict,content,size,layout,style,paint")]
+    #[value_info(other_values = "none,strict,content,size,layout,paint")]
     /// Constants for contain: https://drafts.csswg.org/css-contain/#contain-property
     pub struct Contain: u8 {
         /// 'size' variant, turns on size containment
         const SIZE = 0x01;
         /// `layout` variant, turns on layout containment
         const LAYOUT = 0x02;
-        /// `style` variant, turns on style containment
-        const STYLE = 0x04;
         /// `paint` variant, turns on paint containment
-        const PAINT = 0x08;
+        const PAINT = 0x04;
         /// `strict` variant, turns on all types of containment
-        const STRICT = 0x10;
-        /// 'content' variant, turns on style, layout, and paint containment
-        const CONTENT = 0x20;
+        const STRICT = 0x08;
+        /// 'content' variant, turns on layout and paint containment
+        const CONTENT = 0x10;
         /// variant with all the bits that contain: strict turns on
-        const STRICT_BITS = Contain::LAYOUT.bits | Contain::STYLE.bits | Contain::PAINT.bits | Contain::SIZE.bits;
+        const STRICT_BITS = Contain::LAYOUT.bits | Contain::PAINT.bits | Contain::SIZE.bits;
         /// variant with all the bits that contain: content turns on
-        const CONTENT_BITS = Contain::STYLE.bits | Contain::LAYOUT.bits | Contain::PAINT.bits;
+        const CONTENT_BITS = Contain::LAYOUT.bits | Contain::PAINT.bits;
     }
 }
 
@@ -803,7 +801,6 @@ impl ToCss for Contain {
         }
         maybe_write_value!(Contain::SIZE => "size");
         maybe_write_value!(Contain::LAYOUT => "layout");
-        maybe_write_value!(Contain::STYLE => "style");
         maybe_write_value!(Contain::PAINT => "paint");
 
         debug_assert!(has_any);
@@ -812,7 +809,7 @@ impl ToCss for Contain {
 }
 
 impl Parse for Contain {
-    /// none | strict | content | [ size || layout || style || paint ]
+    /// none | strict | content | [ size || layout || paint ]
     fn parse<'i, 't>(
         _context: &ParserContext,
         input: &mut Parser<'i, 't>,
@@ -822,7 +819,6 @@ impl Parse for Contain {
             let flag = match_ignore_ascii_case! { &name,
                 "size" => Some(Contain::SIZE),
                 "layout" => Some(Contain::LAYOUT),
-                "style" => Some(Contain::STYLE),
                 "paint" => Some(Contain::PAINT),
                 "strict" if result.is_empty() => return Ok(Contain::STRICT | Contain::STRICT_BITS),
                 "content" if result.is_empty() => return Ok(Contain::CONTENT | Contain::CONTENT_BITS),
diff --git a/components/style/values/specified/color.rs b/components/style/values/specified/color.rs
index 7a42e834236..9ef9ab57f0a 100644
--- a/components/style/values/specified/color.rs
+++ b/components/style/values/specified/color.rs
@@ -351,13 +351,13 @@ impl Color {
             Color::Special(special) => {
                 use self::gecko::SpecialColorKeyword as Keyword;
                 _context.map(|context| {
-                    let pres_context = context.device().pres_context();
+                    let prefs = context.device().pref_sheet_prefs();
                     convert_nscolor_to_computedcolor(match special {
-                        Keyword::MozDefaultColor => pres_context.mDefaultColor,
-                        Keyword::MozDefaultBackgroundColor => pres_context.mBackgroundColor,
-                        Keyword::MozHyperlinktext => pres_context.mLinkColor,
-                        Keyword::MozActivehyperlinktext => pres_context.mActiveLinkColor,
-                        Keyword::MozVisitedhyperlinktext => pres_context.mVisitedLinkColor,
+                        Keyword::MozDefaultColor => prefs.mDefaultColor,
+                        Keyword::MozDefaultBackgroundColor => prefs.mDefaultBackgroundColor,
+                        Keyword::MozHyperlinktext => prefs.mLinkColor,
+                        Keyword::MozActivehyperlinktext => prefs.mActiveLinkColor,
+                        Keyword::MozVisitedhyperlinktext => prefs.mVisitedLinkColor,
                     })
                 })
             },
diff --git a/components/style/values/specified/effects.rs b/components/style/values/specified/effects.rs
index 42ec0ce0005..38a53749605 100644
--- a/components/style/values/specified/effects.rs
+++ b/components/style/values/specified/effects.rs
@@ -20,6 +20,7 @@ use crate::values::specified::url::SpecifiedUrl;
 use crate::values::specified::{Angle, NumberOrPercentage};
 #[cfg(not(feature = "gecko"))]
 use crate::values::Impossible;
+use crate::Zero;
 use cssparser::{self, BasicParseErrorKind, Parser, Token};
 use style_traits::{ParseError, StyleParseErrorKind, ValueParseErrorKind};
 
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index ffdd8d026ef..acee43f4b38 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -14,11 +14,11 @@ use crate::values::generics::length as generics;
 use crate::values::generics::length::{
     GenericLengthOrNumber, MaxSize as GenericMaxSize, Size as GenericSize,
 };
-use crate::values::generics::transform::IsZeroLength;
 use crate::values::generics::NonNegative;
 use crate::values::specified::calc::CalcNode;
 use crate::values::specified::NonNegativeNumber;
-use crate::values::{Auto, CSSFloat, Either, Normal};
+use crate::values::{CSSFloat, Either, Normal};
+use crate::Zero;
 use app_units::Au;
 use cssparser::{Parser, Token};
 use euclid::Size2D;
@@ -477,21 +477,6 @@ impl NoCalcLength {
         })
     }
 
-    #[inline]
-    /// Returns a `zero` length.
-    pub fn zero() -> NoCalcLength {
-        NoCalcLength::Absolute(AbsoluteLength::Px(0.))
-    }
-
-    #[inline]
-    /// Checks whether the length value is zero.
-    pub fn is_zero(&self) -> bool {
-        match *self {
-            NoCalcLength::Absolute(length) => length.is_zero(),
-            _ => false,
-        }
-    }
-
     /// Get a px value without context.
     #[inline]
     pub fn to_computed_pixel_length_without_context(&self) -> Result<CSSFloat, ()> {
@@ -510,9 +495,12 @@ impl NoCalcLength {
 
 impl SpecifiedValueInfo for NoCalcLength {}
 
-impl IsZeroLength for NoCalcLength {
-    #[inline]
-    fn is_zero_length(&self) -> bool {
+impl Zero for NoCalcLength {
+    fn zero() -> Self {
+        NoCalcLength::Absolute(AbsoluteLength::Px(0.))
+    }
+
+    fn is_zero(&self) -> bool {
         match *self {
             NoCalcLength::Absolute(v) => v.is_zero(),
             NoCalcLength::FontRelative(v) => v.is_zero(),
@@ -585,12 +573,6 @@ impl Mul<CSSFloat> for ViewportPercentageLength {
 
 impl Length {
     #[inline]
-    /// Returns a `zero` length.
-    pub fn zero() -> Length {
-        Length::NoCalc(NoCalcLength::zero())
-    }
-
-    #[inline]
     fn parse_internal<'i, 't>(
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
@@ -672,6 +654,21 @@ impl Parse for Length {
     }
 }
 
+impl Zero for Length {
+    fn zero() -> Self {
+        Length::NoCalc(NoCalcLength::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        // FIXME(emilio): Seems a bit weird to treat calc() unconditionally as
+        // non-zero here?
+        match *self {
+            Length::NoCalc(ref l) => l.is_zero(),
+            Length::Calc(..) => false,
+        }
+    }
+}
+
 impl Length {
     /// Parses a length, with quirks.
     pub fn parse_quirky<'i, 't>(
@@ -711,12 +708,6 @@ impl From<Length> for NonNegativeLength {
 }
 
 impl NonNegativeLength {
-    /// Returns a `zero` length.
-    #[inline]
-    pub fn zero() -> Self {
-        Length::zero().into()
-    }
-
     /// Get an absolute length from a px value.
     #[inline]
     pub fn from_px(px_value: CSSFloat) -> Self {
@@ -738,9 +729,6 @@ impl NonNegativeLength {
     }
 }
 
-/// Either a NonNegativeLength or the `auto` keyword.
-pub type NonNegativeLengthOrAuto = Either<NonNegativeLength, Auto>;
-
 /// A `<length-percentage>` value. This can be either a `<length>`, a
 /// `<percentage>`, or a combination of both via `calc()`.
 ///
@@ -802,12 +790,6 @@ impl Parse for LengthPercentage {
 
 impl LengthPercentage {
     #[inline]
-    /// Returns a `zero` length.
-    pub fn zero() -> LengthPercentage {
-        LengthPercentage::Length(NoCalcLength::zero())
-    }
-
-    #[inline]
     /// Returns a `0%` value.
     pub fn zero_percent() -> LengthPercentage {
         LengthPercentage::Percentage(computed::Percentage::zero())
@@ -898,11 +880,14 @@ impl LengthPercentage {
     }
 }
 
-impl IsZeroLength for LengthPercentage {
-    #[inline]
-    fn is_zero_length(&self) -> bool {
+impl Zero for LengthPercentage {
+    fn zero() -> Self {
+        LengthPercentage::Length(NoCalcLength::zero())
+    }
+
+    fn is_zero(&self) -> bool {
         match *self {
-            LengthPercentage::Length(l) => l.is_zero_length(),
+            LengthPercentage::Length(l) => l.is_zero(),
             LengthPercentage::Percentage(p) => p.0 == 0.0,
             LengthPercentage::Calc(_) => false,
         }
@@ -913,11 +898,6 @@ impl IsZeroLength for LengthPercentage {
 pub type LengthPercentageOrAuto = generics::LengthPercentageOrAuto<LengthPercentage>;
 
 impl LengthPercentageOrAuto {
-    /// Returns a value representing a `0` length.
-    pub fn zero() -> Self {
-        generics::LengthPercentageOrAuto::LengthPercentage(LengthPercentage::zero())
-    }
-
     /// Returns a value representing `0%`.
     #[inline]
     pub fn zero_percent() -> Self {
@@ -943,11 +923,6 @@ pub type NonNegativeLengthPercentageOrAuto =
     generics::LengthPercentageOrAuto<NonNegativeLengthPercentage>;
 
 impl NonNegativeLengthPercentageOrAuto {
-    /// Returns a value representing a `0` length.
-    pub fn zero() -> Self {
-        generics::LengthPercentageOrAuto::LengthPercentage(NonNegativeLengthPercentage::zero())
-    }
-
     /// Returns a value representing `0%`.
     #[inline]
     pub fn zero_percent() -> Self {
@@ -998,12 +973,6 @@ impl Parse for NonNegativeLengthPercentage {
 
 impl NonNegativeLengthPercentage {
     #[inline]
-    /// Returns a `zero` length.
-    pub fn zero() -> Self {
-        NonNegative(LengthPercentage::zero())
-    }
-
-    #[inline]
     /// Returns a `0%` value.
     pub fn zero_percent() -> Self {
         NonNegative(LengthPercentage::zero_percent())
@@ -1025,7 +994,29 @@ impl NonNegativeLengthPercentage {
 pub type LengthOrNormal = Either<Length, Normal>;
 
 /// Either a `<length>` or the `auto` keyword.
-pub type LengthOrAuto = Either<Length, Auto>;
+///
+/// Note that we use LengthPercentage just for convenience, since it pretty much
+/// is everything we care about, but we could just add a similar LengthOrAuto
+/// instead if we think getting rid of this weirdness is worth it.
+pub type LengthOrAuto = generics::LengthPercentageOrAuto<Length>;
+
+impl LengthOrAuto {
+    /// Parses a length, allowing the unitless length quirk.
+    /// <https://quirks.spec.whatwg.org/#the-unitless-length-quirk>
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with(context, input, |context, input| {
+            Length::parse_quirky(context, input, allow_quirks)
+        })
+    }
+}
+
+/// Either a non-negative `<length>` or the `auto` keyword.
+pub type NonNegativeLengthOrAuto = generics::LengthPercentageOrAuto<NonNegativeLength>;
 
 /// Either a `<length>` or a `<number>`.
 pub type LengthOrNumber = GenericLengthOrNumber<Length, Number>;
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 4956d53f177..7295f060697 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -11,7 +11,7 @@ use super::computed::{Context, ToComputedValue};
 use super::generics::grid::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
 use super::generics::grid::{TrackList as GenericTrackList, TrackSize as GenericTrackSize};
 use super::generics::transform::IsParallelTo;
-use super::generics::{GreaterThanOrEqualToOne, NonNegative};
+use super::generics::{self, GreaterThanOrEqualToOne, NonNegative};
 use super::{Auto, CSSFloat, CSSInteger, Either};
 use crate::context::QuirksMode;
 use crate::parser::{Parse, ParserContext};
@@ -60,7 +60,7 @@ pub use self::image::{ColorStop, EndingShape as GradientEndingShape, Gradient};
 pub use self::image::{GradientItem, GradientKind, Image, ImageLayer, MozImageRect};
 pub use self::length::{AbsoluteLength, CalcLengthPercentage, CharacterWidth};
 pub use self::length::{FontRelativeLength, Length, LengthOrNumber, NonNegativeLengthOrNumber};
-pub use self::length::{LengthPercentage, LengthPercentageOrAuto};
+pub use self::length::{LengthOrAuto, LengthPercentage, LengthPercentageOrAuto};
 pub use self::length::{MaxSize, Size};
 pub use self::length::{NoCalcLength, ViewportPercentageLength};
 pub use self::length::{NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto};
@@ -80,7 +80,7 @@ pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::svg_path::SVGPathData;
 pub use self::table::XSpan;
 pub use self::text::{InitialLetter, LetterSpacing, LineHeight, TextAlign};
-pub use self::text::{OverflowWrap, TextEmphasisPosition, TextEmphasisStyle};
+pub use self::text::{OverflowWrap, TextEmphasisPosition, TextEmphasisStyle, WordBreak};
 pub use self::text::{TextAlignKeyword, TextDecorationLine, TextOverflow, WordSpacing};
 pub use self::time::Time;
 pub use self::transform::{Rotate, Scale, Transform};
@@ -605,99 +605,8 @@ pub type GridLine = GenericGridLine<Integer>;
 /// `<grid-template-rows> | <grid-template-columns>`
 pub type GridTemplateComponent = GenericGridTemplateComponent<LengthPercentage, Integer>;
 
-#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo)]
-/// rect(<top>, <left>, <bottom>, <right>) used by clip and image-region
-#[css(function = "rect")]
-pub struct ClipRect {
-    /// <top> (<length> | <auto>)
-    pub top: Option<Length>,
-    /// <right> (<length> | <auto>)
-    pub right: Option<Length>,
-    /// <bottom> (<length> | <auto>)
-    pub bottom: Option<Length>,
-    /// <left> (<length> | <auto>)
-    pub left: Option<Length>,
-}
-
-impl ToCss for ClipRect {
-    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
-    where
-        W: Write,
-    {
-        dest.write_str("rect(")?;
-
-        if let Some(ref top) = self.top {
-            top.to_css(dest)?;
-            dest.write_str(", ")?;
-        } else {
-            dest.write_str("auto, ")?;
-        }
-
-        if let Some(ref right) = self.right {
-            right.to_css(dest)?;
-            dest.write_str(", ")?;
-        } else {
-            dest.write_str("auto, ")?;
-        }
-
-        if let Some(ref bottom) = self.bottom {
-            bottom.to_css(dest)?;
-            dest.write_str(", ")?;
-        } else {
-            dest.write_str("auto, ")?;
-        }
-
-        if let Some(ref left) = self.left {
-            left.to_css(dest)?;
-        } else {
-            dest.write_str("auto")?;
-        }
-
-        dest.write_str(")")?;
-        Ok(())
-    }
-}
-
-impl ToComputedValue for ClipRect {
-    type ComputedValue = super::computed::ClipRect;
-
-    #[inline]
-    fn to_computed_value(&self, context: &Context) -> super::computed::ClipRect {
-        super::computed::ClipRect {
-            top: self.top.as_ref().map(|top| top.to_computed_value(context)),
-            right: self
-                .right
-                .as_ref()
-                .map(|right| right.to_computed_value(context)),
-            bottom: self
-                .bottom
-                .as_ref()
-                .map(|bottom| bottom.to_computed_value(context)),
-            left: self
-                .left
-                .as_ref()
-                .map(|left| left.to_computed_value(context)),
-        }
-    }
-
-    #[inline]
-    fn from_computed_value(computed: &super::computed::ClipRect) -> Self {
-        ClipRect {
-            top: computed
-                .top
-                .map(|top| ToComputedValue::from_computed_value(&top)),
-            right: computed
-                .right
-                .map(|right| ToComputedValue::from_computed_value(&right)),
-            bottom: computed
-                .bottom
-                .map(|bottom| ToComputedValue::from_computed_value(&bottom)),
-            left: computed
-                .left
-                .map(|left| ToComputedValue::from_computed_value(&left)),
-        }
-    }
-}
+/// rect(...)
+pub type ClipRect = generics::ClipRect<LengthOrAuto>;
 
 impl Parse for ClipRect {
     fn parse<'i, 't>(
@@ -715,25 +624,16 @@ impl ClipRect {
         input: &mut Parser<'i, 't>,
         allow_quirks: AllowQuirks,
     ) -> Result<Self, ParseError<'i>> {
-        use crate::values::specified::Length;
+        input.expect_function_matching("rect")?;
 
         fn parse_argument<'i, 't>(
             context: &ParserContext,
             input: &mut Parser<'i, 't>,
             allow_quirks: AllowQuirks,
-        ) -> Result<Option<Length>, ParseError<'i>> {
-            if input
-                .try(|input| input.expect_ident_matching("auto"))
-                .is_ok()
-            {
-                Ok(None)
-            } else {
-                Length::parse_quirky(context, input, allow_quirks).map(Some)
-            }
+        ) -> Result<LengthOrAuto, ParseError<'i>> {
+            LengthOrAuto::parse_quirky(context, input, allow_quirks)
         }
 
-        input.expect_function_matching("rect")?;
-
         input.parse_nested_block(|input| {
             let top = parse_argument(context, input, allow_quirks)?;
             let right;
@@ -751,11 +651,12 @@ impl ClipRect {
                 bottom = parse_argument(context, input, allow_quirks)?;
                 left = parse_argument(context, input, allow_quirks)?;
             }
+
             Ok(ClipRect {
-                top: top,
-                right: right,
-                bottom: bottom,
-                left: left,
+                top,
+                right,
+                bottom,
+                left,
             })
         })
     }
@@ -782,16 +683,22 @@ impl ClipRectOrAuto {
 /// Whether quirks are allowed in this context.
 #[derive(Clone, Copy, PartialEq)]
 pub enum AllowQuirks {
-    /// Quirks are allowed.
-    Yes,
     /// Quirks are not allowed.
     No,
+    /// Quirks are allowed, in quirks mode.
+    Yes,
+    /// Quirks are always allowed, used for SVG lengths.
+    Always,
 }
 
 impl AllowQuirks {
     /// Returns `true` if quirks are allowed in this context.
     pub fn allowed(self, quirks_mode: QuirksMode) -> bool {
-        self == AllowQuirks::Yes && quirks_mode == QuirksMode::Quirks
+        match self {
+            AllowQuirks::Always => true,
+            AllowQuirks::No => false,
+            AllowQuirks::Yes => quirks_mode == QuirksMode::Quirks,
+        }
     }
 }
 
diff --git a/components/style/values/specified/position.rs b/components/style/values/specified/position.rs
index 0212763ec6d..f60767f1656 100644
--- a/components/style/values/specified/position.rs
+++ b/components/style/values/specified/position.rs
@@ -17,6 +17,7 @@ use crate::values::generics::position::ZIndex as GenericZIndex;
 use crate::values::specified::transform::OriginComponent;
 use crate::values::specified::{AllowQuirks, Integer, LengthPercentage};
 use crate::values::{Either, None_};
+use crate::Zero;
 use cssparser::Parser;
 use selectors::parser::SelectorParseErrorKind;
 use servo_arc::Arc;
diff --git a/components/style/values/specified/svg.rs b/components/style/values/specified/svg.rs
index 98db273e61c..556e995c02f 100644
--- a/components/style/values/specified/svg.rs
+++ b/components/style/values/specified/svg.rs
@@ -8,9 +8,9 @@ use crate::parser::{Parse, ParserContext};
 use crate::values::generics::svg as generic;
 use crate::values::specified::color::Color;
 use crate::values::specified::url::SpecifiedUrl;
+use crate::values::specified::AllowQuirks;
 use crate::values::specified::LengthPercentage;
-use crate::values::specified::{NonNegativeLengthPercentage, NonNegativeNumber};
-use crate::values::specified::{Number, Opacity};
+use crate::values::specified::{NonNegativeLengthPercentage, Opacity};
 use crate::values::CustomIdent;
 use cssparser::Parser;
 use std::fmt::{self, Write};
@@ -23,36 +23,52 @@ pub type SVGPaint = generic::SVGPaint<Color, SpecifiedUrl>;
 /// Specified SVG Paint Kind value
 pub type SVGPaintKind = generic::SVGPaintKind<Color, SpecifiedUrl>;
 
-/// A value of <length> | <percentage> | <number> for stroke-dashoffset.
-/// <https://www.w3.org/TR/SVG11/painting.html#StrokeProperties>
-pub type SvgLengthPercentageOrNumber =
-    generic::SvgLengthPercentageOrNumber<LengthPercentage, Number>;
-
 /// <length> | <percentage> | <number> | context-value
-pub type SVGLength = generic::SVGLength<SvgLengthPercentageOrNumber>;
+pub type SVGLength = generic::SVGLength<LengthPercentage>;
 
-impl From<SvgLengthPercentageOrNumber> for SVGLength {
-    fn from(length: SvgLengthPercentageOrNumber) -> Self {
-        generic::SVGLength::Length(length)
-    }
+/// A non-negative version of SVGLength.
+pub type SVGWidth = generic::SVGLength<NonNegativeLengthPercentage>;
+
+/// [ <length> | <percentage> | <number> ]# | context-value
+pub type SVGStrokeDashArray = generic::SVGStrokeDashArray<NonNegativeLengthPercentage>;
+
+/// Whether the `context-value` value is enabled.
+#[cfg(feature = "gecko")]
+pub fn is_context_value_enabled() -> bool {
+    use crate::gecko_bindings::structs::mozilla;
+    unsafe { mozilla::StaticPrefs_sVarCache_gfx_font_rendering_opentype_svg_enabled }
 }
 
-/// A value of <length> | <percentage> | <number> for stroke-width/stroke-dasharray.
-/// <https://www.w3.org/TR/SVG11/painting.html#StrokeProperties>
-pub type NonNegativeSvgLengthPercentageOrNumber =
-    generic::SvgLengthPercentageOrNumber<NonNegativeLengthPercentage, NonNegativeNumber>;
+/// Whether the `context-value` value is enabled.
+#[cfg(not(feature = "gecko"))]
+pub fn is_context_value_enabled() -> bool {
+    false
+}
 
-/// A non-negative version of SVGLength.
-pub type SVGWidth = generic::SVGLength<NonNegativeSvgLengthPercentageOrNumber>;
+macro_rules! parse_svg_length {
+    ($ty:ty, $lp:ty) => {
+        impl Parse for $ty {
+            fn parse<'i, 't>(
+                context: &ParserContext,
+                input: &mut Parser<'i, 't>,
+            ) -> Result<Self, ParseError<'i>> {
+                if let Ok(lp) = input.try(|i| <$lp>::parse_quirky(context, i, AllowQuirks::Always))
+                {
+                    return Ok(generic::SVGLength::LengthPercentage(lp));
+                }
 
-impl From<NonNegativeSvgLengthPercentageOrNumber> for SVGWidth {
-    fn from(length: NonNegativeSvgLengthPercentageOrNumber) -> Self {
-        generic::SVGLength::Length(length)
-    }
+                try_match_ident_ignore_ascii_case! { input,
+                    "context-value" if is_context_value_enabled() => {
+                        Ok(generic::SVGLength::ContextValue)
+                    },
+                }
+            }
+        }
+    };
 }
 
-/// [ <length> | <percentage> | <number> ]# | context-value
-pub type SVGStrokeDashArray = generic::SVGStrokeDashArray<NonNegativeSvgLengthPercentageOrNumber>;
+parse_svg_length!(SVGLength, LengthPercentage);
+parse_svg_length!(SVGWidth, NonNegativeLengthPercentage);
 
 impl Parse for SVGStrokeDashArray {
     fn parse<'i, 't>(
@@ -61,14 +77,14 @@ impl Parse for SVGStrokeDashArray {
     ) -> Result<Self, ParseError<'i>> {
         if let Ok(values) = input.try(|i| {
             CommaWithSpace::parse(i, |i| {
-                NonNegativeSvgLengthPercentageOrNumber::parse(context, i)
+                NonNegativeLengthPercentage::parse_quirky(context, i, AllowQuirks::Always)
             })
         }) {
             return Ok(generic::SVGStrokeDashArray::Values(values));
         }
 
         try_match_ident_ignore_ascii_case! { input,
-            "context-value" if generic::is_context_value_enabled(context) => {
+            "context-value" if is_context_value_enabled() => {
                 Ok(generic::SVGStrokeDashArray::ContextValue)
             },
             "none" => Ok(generic::SVGStrokeDashArray::Values(vec![])),
diff --git a/components/style/values/specified/text.rs b/components/style/values/specified/text.rs
index 1879dc4159a..883084e649a 100644
--- a/components/style/values/specified/text.rs
+++ b/components/style/values/specified/text.rs
@@ -813,6 +813,33 @@ impl From<TextEmphasisPosition> for u8 {
     }
 }
 
+/// Values for the `word-break` property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+)]
+#[allow(missing_docs)]
+pub enum WordBreak {
+    Normal,
+    BreakAll,
+    KeepAll,
+    /// The break-word value, needed for compat.
+    ///
+    /// Specifying `word-break: break-word` makes `overflow-wrap` behave as
+    /// `anywhere`, and `word-break` behave like `normal`.
+    #[cfg(feature = "gecko")]
+    BreakWord,
+}
+
 /// Values for the `overflow-wrap` property.
 #[repr(u8)]
 #[derive(
diff --git a/components/style/values/specified/transform.rs b/components/style/values/specified/transform.rs
index c4f43735498..92ca953159f 100644
--- a/components/style/values/specified/transform.rs
+++ b/components/style/values/specified/transform.rs
@@ -11,6 +11,7 @@ use crate::values::generics::transform as generic;
 use crate::values::generics::transform::{Matrix, Matrix3D};
 use crate::values::specified::position::{Side, X, Y};
 use crate::values::specified::{self, Angle, Integer, Length, LengthPercentage, Number};
+use crate::Zero;
 use cssparser::Parser;
 use style_traits::{ParseError, StyleParseErrorKind};
 
@@ -108,9 +109,9 @@ impl Transform {
                         let sx = specified::LengthPercentage::parse(context, input)?;
                         if input.try(|input| input.expect_comma()).is_ok() {
                             let sy = specified::LengthPercentage::parse(context, input)?;
-                            Ok(generic::TransformOperation::Translate(sx, Some(sy)))
+                            Ok(generic::TransformOperation::Translate(sx, sy))
                         } else {
-                            Ok(generic::TransformOperation::Translate(sx, None))
+                            Ok(generic::TransformOperation::Translate(sx, Zero::zero()))
                         }
                     },
                     "translatex" => {
@@ -137,9 +138,9 @@ impl Transform {
                         let sx = Number::parse(context, input)?;
                         if input.try(|input| input.expect_comma()).is_ok() {
                             let sy = Number::parse(context, input)?;
-                            Ok(generic::TransformOperation::Scale(sx, Some(sy)))
+                            Ok(generic::TransformOperation::Scale(sx, sy))
                         } else {
-                            Ok(generic::TransformOperation::Scale(sx, None))
+                            Ok(generic::TransformOperation::Scale(sx, sx))
                         }
                     },
                     "scalex" => {
@@ -193,9 +194,9 @@ impl Transform {
                         let ax = specified::Angle::parse_with_unitless(context, input)?;
                         if input.try(|input| input.expect_comma()).is_ok() {
                             let ay = specified::Angle::parse_with_unitless(context, input)?;
-                            Ok(generic::TransformOperation::Skew(ax, Some(ay)))
+                            Ok(generic::TransformOperation::Skew(ax, ay))
                         } else {
-                            Ok(generic::TransformOperation::Skew(ax, None))
+                            Ok(generic::TransformOperation::Skew(ax, Zero::zero()))
                         }
                     },
                     "skewx" => {
diff --git a/components/style_derive/cg.rs b/components/style_derive/cg.rs
index 6eeca384bfa..a5f15a0358e 100644
--- a/components/style_derive/cg.rs
+++ b/components/style_derive/cg.rs
@@ -12,6 +12,70 @@ use syn::{TypeParam, TypeParen, TypePath, TypeSlice, TypeTuple};
 use syn::{Variant, WherePredicate};
 use synstructure::{self, BindStyle, BindingInfo, VariantAst, VariantInfo};
 
+/// Given an input type which has some where clauses already, like:
+///
+/// struct InputType<T>
+/// where
+///     T: Zero,
+/// {
+///     ...
+/// }
+///
+/// Add the necessary `where` clauses so that the output type of a trait
+/// fulfils them.
+///
+/// For example:
+///
+///     <T as ToComputedValue>::ComputedValue: Zero,
+///
+/// This needs to run before adding other bounds to the type parameters.
+pub fn propagate_clauses_to_output_type(
+    where_clause: &mut Option<syn::WhereClause>,
+    generics: &syn::Generics,
+    trait_path: Path,
+    trait_output: Ident,
+) {
+    let where_clause = match *where_clause {
+        Some(ref mut clause) => clause,
+        None => return,
+    };
+    let mut extra_bounds = vec![];
+    for pred in &where_clause.predicates {
+        let ty = match *pred {
+            syn::WherePredicate::Type(ref ty) => ty,
+            ref predicate => panic!("Unhanded complex where predicate: {:?}", predicate),
+        };
+
+        let path = match ty.bounded_ty {
+            syn::Type::Path(ref p) => &p.path,
+            ref ty => panic!("Unhanded complex where type: {:?}", ty),
+        };
+
+        assert!(
+            ty.lifetimes.is_none(),
+            "Unhanded complex lifetime bound: {:?}",
+            ty,
+        );
+
+        let ident = match path_to_ident(path) {
+            Some(i) => i,
+            None => panic!("Unhanded complex where type path: {:?}", path),
+        };
+
+        if generics.type_params().any(|param| param.ident == *ident) {
+            extra_bounds.push(ty.clone());
+        }
+    }
+
+    for bound in extra_bounds {
+        let ty = bound.bounded_ty;
+        let bounds = bound.bounds;
+        where_clause
+            .predicates
+            .push(parse_quote!(<#ty as #trait_path>::#trait_output: #bounds))
+    }
+}
+
 pub fn add_predicate(where_clause: &mut Option<syn::WhereClause>, pred: WherePredicate) {
     where_clause
         .get_or_insert(parse_quote!(where))
diff --git a/components/style_derive/to_animated_value.rs b/components/style_derive/to_animated_value.rs
index b53cf9c3d41..1aba9b3327e 100644
--- a/components/style_derive/to_animated_value.rs
+++ b/components/style_derive/to_animated_value.rs
@@ -9,6 +9,12 @@ use synstructure::BindStyle;
 
 pub fn derive(mut input: DeriveInput) -> TokenStream {
     let mut where_clause = input.generics.where_clause.take();
+    cg::propagate_clauses_to_output_type(
+        &mut where_clause,
+        &input.generics,
+        parse_quote!(crate::values::animated::ToAnimatedValue),
+        parse_quote!(AnimatedValue),
+    );
     for param in input.generics.type_params() {
         cg::add_predicate(
             &mut where_clause,
diff --git a/components/style_derive/to_computed_value.rs b/components/style_derive/to_computed_value.rs
index 68261740502..b0b2aa6af63 100644
--- a/components/style_derive/to_computed_value.rs
+++ b/components/style_derive/to_computed_value.rs
@@ -9,6 +9,12 @@ use synstructure::BindStyle;
 
 pub fn derive(mut input: DeriveInput) -> TokenStream {
     let mut where_clause = input.generics.where_clause.take();
+    cg::propagate_clauses_to_output_type(
+        &mut where_clause,
+        &input.generics,
+        parse_quote!(crate::values::computed::ToComputedValue),
+        parse_quote!(ComputedValue),
+    );
     let (to_body, from_body) = {
         let params = input.generics.type_params().collect::<Vec<_>>();
         for param in &params {
diff --git a/components/style_derive/to_css.rs b/components/style_derive/to_css.rs
index 4eabdcb8357..249ff2969cd 100644
--- a/components/style_derive/to_css.rs
+++ b/components/style_derive/to_css.rs
@@ -148,12 +148,20 @@ fn derive_variant_fields_expr(
                 }
             }
         }
+
+        if let Some(condition) = attrs.contextual_skip_if {
+            expr = quote! {
+                if !#condition(#(#bindings), *) {
+                    #expr
+                }
+            }
+        }
         return expr;
     }
 
-    let mut expr = derive_single_field_expr(first, attrs, where_clause);
+    let mut expr = derive_single_field_expr(first, attrs, where_clause, bindings);
     for (binding, attrs) in iter {
-        derive_single_field_expr(binding, attrs, where_clause).to_tokens(&mut expr)
+        derive_single_field_expr(binding, attrs, where_clause, bindings).to_tokens(&mut expr)
     }
 
     quote! {{
@@ -167,6 +175,7 @@ fn derive_single_field_expr(
     field: &BindingInfo,
     attrs: CssFieldAttrs,
     where_clause: &mut Option<WhereClause>,
+    bindings: &[BindingInfo],
 ) -> TokenStream {
     let mut expr = if attrs.iterable {
         if let Some(if_empty) = attrs.if_empty {
@@ -216,6 +225,14 @@ fn derive_single_field_expr(
         }
     }
 
+    if let Some(condition) = attrs.contextual_skip_if {
+        expr = quote! {
+            if !#condition(#(#bindings), *) {
+                #expr
+            }
+        }
+    }
+
     expr
 }
 
@@ -249,5 +266,6 @@ pub struct CssFieldAttrs {
     pub iterable: bool,
     pub skip: bool,
     pub represents_keyword: bool,
+    pub contextual_skip_if: Option<Path>,
     pub skip_if: Option<Path>,
 }
diff --git a/components/style_traits/values.rs b/components/style_traits/values.rs
index 582e34eb3db..46751541319 100644
--- a/components/style_traits/values.rs
+++ b/components/style_traits/values.rs
@@ -37,6 +37,10 @@ use std::fmt::{self, Write};
 /// * if `#[css(skip_if = "function")]` is found on a field, the `ToCss` call
 ///   for that field is skipped if `function` returns true. This function is
 ///   provided the field as an argument;
+/// * if `#[css(contextual_skip_if = "function")]` is found on a field, the
+///   `ToCss` call for that field is skipped if `function` returns true. This
+///   function is given all the fields in the current struct or variant as an
+///   argument;
 /// * `#[css(represents_keyword)]` can be used on bool fields in order to
 ///   serialize the field name if the field is true, or nothing otherwise.  It
 ///   also collects those keywords for `SpecifiedValueInfo`.
diff --git a/tests/unit/style/animated_properties.rs b/tests/unit/style/animated_properties.rs
index 8fa45a6305f..dd233f01b89 100644
--- a/tests/unit/style/animated_properties.rs
+++ b/tests/unit/style/animated_properties.rs
@@ -92,53 +92,3 @@ fn test_transform_interpolation_on_scale() {
         Transform(vec![TransformOperation::Scale3D(1.5, 3.0, 1.5)])
     );
 }
-
-#[test]
-fn test_transform_interpolation_on_rotate() {
-    use style::values::computed::Angle;
-
-    let from = Transform(vec![TransformOperation::Rotate3D(
-        0.0,
-        0.0,
-        1.0,
-        Angle::from_radians(0.0),
-    )]);
-    let to = Transform(vec![TransformOperation::Rotate3D(
-        0.0,
-        0.0,
-        1.0,
-        Angle::from_radians(100.0),
-    )]);
-    assert_eq!(
-        from.animate(&to, Procedure::Interpolate { progress: 0.5 })
-            .unwrap(),
-        Transform(vec![TransformOperation::Rotate3D(
-            0.0,
-            0.0,
-            1.0,
-            Angle::from_radians(50.0)
-        )])
-    );
-}
-
-#[test]
-fn test_transform_interpolation_on_skew() {
-    use style::values::computed::Angle;
-
-    let from = Transform(vec![TransformOperation::Skew(
-        Angle::from_radians(0.0),
-        Some(Angle::from_radians(100.0)),
-    )]);
-    let to = Transform(vec![TransformOperation::Skew(
-        Angle::from_radians(100.0),
-        Some(Angle::from_radians(0.0)),
-    )]);
-    assert_eq!(
-        from.animate(&to, Procedure::Interpolate { progress: 0.5 })
-            .unwrap(),
-        Transform(vec![TransformOperation::Skew(
-            Angle::from_radians(50.0),
-            Some(Angle::from_radians(50.0)),
-        )])
-    );
-}
diff --git a/tests/unit/style/custom_properties.rs b/tests/unit/style/custom_properties.rs
index b24ca3b132a..5b5741d2690 100644
--- a/tests/unit/style/custom_properties.rs
+++ b/tests/unit/style/custom_properties.rs
@@ -7,30 +7,30 @@ use servo_arc::Arc;
 use style::custom_properties::{
     CssEnvironment, CustomPropertiesBuilder, CustomPropertiesMap, Name, SpecifiedValue,
 };
-use style::properties::CustomDeclarationValue;
+use style::properties::{CustomDeclaration, CustomDeclarationValue};
+use style::stylesheets::Origin;
 use test::{self, Bencher};
 
 fn cascade(
     name_and_value: &[(&str, &str)],
     inherited: Option<&Arc<CustomPropertiesMap>>,
 ) -> Option<Arc<CustomPropertiesMap>> {
-    let values = name_and_value
+    let declarations = name_and_value
         .iter()
         .map(|&(name, value)| {
             let mut input = ParserInput::new(value);
             let mut parser = Parser::new(&mut input);
-            (
-                Name::from(name),
-                SpecifiedValue::parse(&mut parser).unwrap(),
-            )
+            let name = Name::from(name);
+            let value = CustomDeclarationValue::Value(SpecifiedValue::parse(&mut parser).unwrap());
+            CustomDeclaration { name, value }
         })
         .collect::<Vec<_>>();
 
     let env = CssEnvironment;
     let mut builder = CustomPropertiesBuilder::new(inherited, &env);
 
-    for &(ref name, ref val) in &values {
-        builder.cascade(name, &CustomDeclarationValue::Value(val.clone()));
+    for declaration in &declarations {
+        builder.cascade(declaration, Origin::Author);
     }
 
     builder.build()
diff --git a/tests/wpt/metadata/css/css-text/inheritance.html.ini b/tests/wpt/metadata/css/css-text/inheritance.html.ini
index ea3be987a40..a2715f4fe76 100644
--- a/tests/wpt/metadata/css/css-text/inheritance.html.ini
+++ b/tests/wpt/metadata/css/css-text/inheritance.html.ini
@@ -2,6 +2,3 @@
   [Property text-justify inherits]
     expected: FAIL
 
-  [Property word-spacing has initial value 0px]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/css/css-variables/variable-definition-keywords.html.ini b/tests/wpt/metadata/css/css-variables/variable-definition-keywords.html.ini
deleted file mode 100644
index 1759114e0b3..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-definition-keywords.html.ini
+++ /dev/null
@@ -1,7 +0,0 @@
-[variable-definition-keywords.html]
-  [specified style revert]
-    expected: FAIL
-
-  [computed style revert]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/css/css-variables/variable-presentation-attribute.html.ini b/tests/wpt/metadata/css/css-variables/variable-presentation-attribute.html.ini
index bbb64382d67..4e4418a7cce 100644
--- a/tests/wpt/metadata/css/css-variables/variable-presentation-attribute.html.ini
+++ b/tests/wpt/metadata/css/css-variables/variable-presentation-attribute.html.ini
@@ -110,9 +110,6 @@
   [Testing 'visibility'.]
     expected: FAIL
 
-  [Testing 'word-spacing'.]
-    expected: FAIL
-
   [Testing 'writing-mode'.]
     expected: FAIL