style: Fix servo build, and appease tidy / fmt.

23 files changed, 165 insertions, 53 deletions

diff --git a/Cargo.lock b/Cargo.lock
index ea625f81909..8164783500d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -943,6 +943,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "derive_common"
+version = "0.0.1"
+dependencies = [
+ "darling 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 0.4.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "synstructure 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "derive_more"
 version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -3646,6 +3657,8 @@ dependencies = [
  "servo_arc 0.1.1",
  "smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "thin-slice 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "to_shmem 0.0.1",
+ "to_shmem_derive 0.0.1",
 ]
 
 [[package]]
@@ -3992,6 +4005,8 @@ dependencies = [
  "malloc_size_of_derive 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.80 (registry+https://github.com/rust-lang/crates.io-index)",
  "servo_rand 0.0.1",
+ "to_shmem 0.0.1",
+ "to_shmem_derive 0.0.1",
  "url 1.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "url_serde 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "uuid 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4240,6 +4255,8 @@ dependencies = [
  "style_traits 0.0.1",
  "thin-slice 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)",
+ "to_shmem 0.0.1",
+ "to_shmem_derive 0.0.1",
  "toml 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "uluru 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-bidi 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4253,6 +4270,7 @@ name = "style_derive"
 version = "0.0.1"
 dependencies = [
  "darling 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "derive_common 0.0.1",
  "proc-macro2 0.4.26 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4297,6 +4315,8 @@ dependencies = [
  "servo_arc 0.1.1",
  "servo_atoms 0.0.1",
  "servo_url 0.0.1",
+ "to_shmem 0.0.1",
+ "to_shmem_derive 0.0.1",
  "webrender_api 0.60.0 (git+https://github.com/servo/webrender)",
 ]
 
@@ -4436,6 +4456,31 @@ dependencies = [
 ]
 
 [[package]]
+name = "to_shmem"
+version = "0.0.1"
+dependencies = [
+ "cssparser 0.25.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.80 (registry+https://github.com/rust-lang/crates.io-index)",
+ "servo_arc 0.1.1",
+ "smallbitvec 2.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thin-slice 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "to_shmem_derive"
+version = "0.0.1"
+dependencies = [
+ "darling 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "derive_common 0.0.1",
+ "proc-macro2 0.4.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.15.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "synstructure 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "tokio"
 version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/components/gfx/font.rs b/components/gfx/font.rs
index cd9513a3f43..35ce19621ac 100644
--- a/components/gfx/font.rs
+++ b/components/gfx/font.rs
@@ -26,7 +26,7 @@ use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 use style::computed_values::{font_stretch, font_style, font_variant_caps, font_weight};
 use style::properties::style_structs::Font as FontStyleStruct;
-use style::values::computed::font::SingleFontFamily;
+use style::values::computed::font::{GenericFontFamily, SingleFontFamily};
 use unicode_script::Script;
 
 macro_rules! ot_tag {
@@ -564,9 +564,14 @@ impl<'a> From<&'a SingleFontFamily> for FontFamilyName {
                 FontFamilyName::Specific(family_name.name.clone())
             },
 
-            SingleFontFamily::Generic(ref generic_name) => {
-                FontFamilyName::Generic(generic_name.clone())
-            },
+            SingleFontFamily::Generic(generic) => FontFamilyName::Generic(match generic {
+                GenericFontFamily::None => panic!("Shouldn't appear in style"),
+                GenericFontFamily::Serif => atom!("serif"),
+                GenericFontFamily::SansSerif => atom!("sans-serif"),
+                GenericFontFamily::Monospace => atom!("monospace"),
+                GenericFontFamily::Cursive => atom!("cursive"),
+                GenericFontFamily::Fantasy => atom!("fantasy"),
+            }),
         }
     }
 }
diff --git a/components/layout/multicol.rs b/components/layout/multicol.rs
index f8ddfa8200c..46ccbc64653 100644
--- a/components/layout/multicol.rs
+++ b/components/layout/multicol.rs
@@ -19,9 +19,10 @@ use std::fmt;
 use std::sync::Arc;
 use style::logical_geometry::LogicalSize;
 use style::properties::ComputedValues;
-use style::values::computed::length::{MaxSize, NonNegativeLengthOrAuto, Size};
+use style::values::computed::length::{
+    MaxSize, NonNegativeLengthOrAuto, NonNegativeLengthPercentageOrNormal, Size,
+};
 use style::values::generics::column::ColumnCount;
-use style::values::Either;
 
 #[allow(unsafe_code)]
 unsafe impl crate::flow::HasBaseFlow for MulticolFlow {}
@@ -106,8 +107,10 @@ impl Flow for MulticolFlow {
         {
             let style = &self.block_flow.fragment.style;
             let column_gap = match style.get_position().column_gap {
-                Either::First(len) => len.0.to_pixel_length(content_inline_size).into(),
-                Either::Second(_normal) => {
+                NonNegativeLengthPercentageOrNormal::LengthPercentage(len) => {
+                    len.0.to_pixel_length(content_inline_size).into()
+                },
+                NonNegativeLengthPercentageOrNormal::Normal => {
                     self.block_flow.fragment.style.get_font().font_size.size()
                 },
             };
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index eb48c22865b..6da5d92fdb1 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -643,6 +643,7 @@ impl LayoutElementHelpers for LayoutDom<Element> {
         };
 
         if let Some(font_family) = font_family {
+            // FIXME(emilio): This in Gecko parses a whole family list.
             hints.push(from_declaration(
                 shared_lock,
                 PropertyDeclaration::FontFamily(font_family::SpecifiedValue::Values(
diff --git a/components/style/Cargo.toml b/components/style/Cargo.toml
index 005924cec21..0bc745015fd 100644
--- a/components/style/Cargo.toml
+++ b/components/style/Cargo.toml
@@ -20,7 +20,7 @@ gecko = ["style_traits/gecko", "fallible/known_system_malloc"]
 use_bindgen = ["bindgen", "regex", "toml"]
 servo = ["serde", "style_traits/servo", "servo_atoms", "servo_config", "html5ever",
          "cssparser/serde", "encoding_rs", "malloc_size_of/servo", "arrayvec/use_union",
-         "servo_url", "string_cache", "crossbeam-channel"]
+         "servo_url", "string_cache", "crossbeam-channel", "to_shmem/servo", "servo_arc/servo"]
 gecko_debug = []
 
 [dependencies]
diff --git a/components/style/font_metrics.rs b/components/style/font_metrics.rs
index a45ebc297d9..8e69118ade4 100644
--- a/components/style/font_metrics.rs
+++ b/components/style/font_metrics.rs
@@ -70,7 +70,7 @@ impl FontMetricsProvider for ServoMetricsProvider {
         ServoMetricsProvider
     }
 
-    fn get_size(&self, _font_name: &Atom, _font_family: u8) -> Au {
+    fn get_size(&self, _: &Atom, _: crate::values::computed::font::GenericFontFamily) -> Au {
         unreachable!("Dummy provider should never be used to compute font size")
     }
 }
diff --git a/components/style/gecko/url.rs b/components/style/gecko/url.rs
index 2c61ab4db0b..2da16043779 100644
--- a/components/style/gecko/url.rs
+++ b/components/style/gecko/url.rs
@@ -123,7 +123,7 @@ impl MallocSizeOf for CssUrl {
 }
 
 /// A key type for URL_VALUE_TABLE.
-#[derive(Hash, PartialEq, Eq)]
+#[derive(Eq, Hash, PartialEq)]
 struct CssUrlDataKey(*const CssUrlData);
 
 unsafe impl Sync for CssUrlDataKey {}
diff --git a/components/style/properties/declaration_block.rs b/components/style/properties/declaration_block.rs
index c86f5bac9ee..42fc833e4b9 100644
--- a/components/style/properties/declaration_block.rs
+++ b/components/style/properties/declaration_block.rs
@@ -25,7 +25,7 @@ use style_traits::{CssWriter, ParseError, ParsingMode, StyleParseErrorKind, ToCs
 use crate::stylesheets::{CssRuleType, Origin, UrlExtraData};
 use super::*;
 use crate::values::computed::Context;
-use crate::selector_parser::{SelectorImpl};
+use crate::selector_parser::SelectorImpl;
 use selectors::SelectorList;
 
 /// The animation rules.
diff --git a/components/style/properties/longhands/font.mako.rs b/components/style/properties/longhands/font.mako.rs
index 7f7b66c3572..c1d3d8fcc6c 100644
--- a/components/style/properties/longhands/font.mako.rs
+++ b/components/style/properties/longhands/font.mako.rs
@@ -495,8 +495,7 @@ ${helpers.predefined_type(
         // a lot of code with `if product == gecko` conditionals, we have a
         // dummy system font module that does nothing
 
-        #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, SpecifiedValueInfo, ToCss)]
-        #[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+        #[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
         /// void enum for system font, can never exist
         pub enum SystemFont {}
         impl SystemFont {
diff --git a/components/style/servo/selector_parser.rs b/components/style/servo/selector_parser.rs
index 229f7dccdd2..d839654a65a 100644
--- a/components/style/servo/selector_parser.rs
+++ b/components/style/servo/selector_parser.rs
@@ -29,8 +29,7 @@ use style_traits::{ParseError, StyleParseErrorKind};
 /// A pseudo-element, both public and private.
 ///
 /// NB: If you add to this list, be sure to update `each_simple_pseudo_element` too.
-#[derive(Clone, Debug, Eq, Hash, PartialEq)]
-#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToShmem)]
 #[allow(missing_docs)]
 #[repr(usize)]
 pub enum PseudoElement {
@@ -265,8 +264,7 @@ pub type Lang = Box<str>;
 
 /// A non tree-structural pseudo-class.
 /// See https://drafts.csswg.org/selectors-4/#structural-pseudos
-#[derive(Clone, Debug, Eq, Hash, PartialEq)]
-#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToShmem)]
 #[allow(missing_docs)]
 pub enum NonTSPseudoClass {
     Active,
diff --git a/components/style/servo/url.rs b/components/style/servo/url.rs
index 26608de2e29..fd7726289be 100644
--- a/components/style/servo/url.rs
+++ b/components/style/servo/url.rs
@@ -12,7 +12,7 @@ use std::fmt::{self, Write};
 // nonzero optimization is important in keeping the size of SpecifiedUrl below
 // the threshold.
 use crate::values::computed::{Context, ToComputedValue};
-use std::sync::Arc;
+use servo_arc::Arc;
 use style_traits::{CssWriter, ParseError, ToCss};
 
 /// A CSS url() value for servo.
@@ -26,7 +26,7 @@ use style_traits::{CssWriter, ParseError, ToCss};
 ///
 /// TODO(emilio): This should be shrunk by making CssUrl a wrapper type of an
 /// arc, and keep the serialization in that Arc. See gecko/url.rs for example.
-#[derive(Clone, Debug, Deserialize, MallocSizeOf, Serialize, SpecifiedValueInfo)]
+#[derive(Clone, Debug, Deserialize, MallocSizeOf, Serialize, SpecifiedValueInfo, ToShmem)]
 pub struct CssUrl {
     /// The original URI. This might be optional since we may insert computed
     /// values of images into the cascade directly, and we don't bother to
diff --git a/components/style/shared_lock.rs b/components/style/shared_lock.rs
index f5019326ee0..073c696fa3d 100644
--- a/components/style/shared_lock.rs
+++ b/components/style/shared_lock.rs
@@ -15,7 +15,6 @@ use std::cell::UnsafeCell;
 use std::fmt;
 #[cfg(feature = "servo")]
 use std::mem;
-#[cfg(feature = "gecko")]
 use std::mem::ManuallyDrop;
 #[cfg(feature = "gecko")]
 use std::ptr;
@@ -124,11 +123,7 @@ impl<'a> Drop for SharedRwLockReadGuard<'a> {
     fn drop(&mut self) {
         // Unsafe: self.lock is private to this module, only ever set after `read()`,
         // and never copied or cloned (see `compile_time_assert` below).
-        if let Some(arc) = self.0.arc {
-            unsafe {
-                arc.force_unlock_read();
-            }
-        }
+        unsafe { self.0.arc.force_unlock_read() }
     }
 }
 
@@ -166,12 +161,6 @@ impl<T: fmt::Debug> fmt::Debug for Locked<T> {
 }
 
 impl<T> Locked<T> {
-    #[cfg(feature = "servo")]
-    #[inline]
-    fn is_read_only_lock(&self) -> bool {
-        false
-    }
-
     #[cfg(feature = "gecko")]
     #[inline]
     fn is_read_only_lock(&self) -> bool {
@@ -199,10 +188,14 @@ impl<T> Locked<T> {
 
     /// Access the data for reading.
     pub fn read_with<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> &'a T {
+        #[cfg(feature = "gecko")]
         assert!(
             self.is_read_only_lock() || self.same_lock_as(guard.0.as_ref().map(|r| &**r)),
             "Locked::read_with called with a guard from an unrelated SharedRwLock"
         );
+        #[cfg(not(feature = "gecko"))]
+        assert!(self.same_lock_as(&guard.0));
+
         let ptr = self.data.get();
 
         // Unsafe:
@@ -223,10 +216,14 @@ impl<T> Locked<T> {
 
     /// Access the data for writing.
     pub fn write_with<'a>(&'a self, guard: &'a mut SharedRwLockWriteGuard) -> &'a mut T {
+        #[cfg(feature = "gecko")]
         assert!(
             !self.is_read_only_lock() && self.same_lock_as(Some(&guard.0)),
             "Locked::write_with called with a guard from a read only or unrelated SharedRwLock"
         );
+        #[cfg(not(feature = "gecko"))]
+        assert!(self.same_lock_as(&guard.0));
+
         let ptr = self.data.get();
 
         // Unsafe:
diff --git a/components/style/stylesheets/mod.rs b/components/style/stylesheets/mod.rs
index 133b84fa52f..16842021e8d 100644
--- a/components/style/stylesheets/mod.rs
+++ b/components/style/stylesheets/mod.rs
@@ -39,6 +39,7 @@ use std::fmt;
 #[cfg(feature = "gecko")]
 use std::mem::{self, ManuallyDrop};
 use style_traits::ParsingMode;
+#[cfg(feature = "gecko")]
 use to_shmem::{SharedMemoryBuilder, ToShmem};
 
 pub use self::counter_style_rule::CounterStyleRule;
diff --git a/components/style/values/computed/font.rs b/components/style/values/computed/font.rs
index 001b8444a30..407a547013f 100644
--- a/components/style/values/computed/font.rs
+++ b/components/style/values/computed/font.rs
@@ -29,6 +29,7 @@ use std::mem::{self, ManuallyDrop};
 #[cfg(feature = "servo")]
 use std::slice;
 use style_traits::{CssWriter, ParseError, ToCss};
+#[cfg(feature = "gecko")]
 use to_shmem::{SharedMemoryBuilder, ToShmem};
 
 pub use crate::values::computed::Length as MozScriptMinSize;
@@ -284,7 +285,7 @@ pub enum FontFamilyNameSyntax {
     Identifiers,
 }
 
-#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, ToCss, ToResolvedValue)]
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, ToCss, ToResolvedValue, ToShmem)]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize, Hash))]
 /// A set of faces that vary in weight, width or slope.
 pub enum SingleFontFamily {
@@ -299,7 +300,10 @@ pub enum SingleFontFamily {
 /// The order here is important, if you change it make sure that
 /// `gfxPlatformFontList.h`s ranged array and `gfxFontFamilyList`'s
 /// sSingleGenerics are updated as well.
-#[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, PartialEq, Parse, ToCss, ToResolvedValue)]
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, PartialEq, Parse, ToCss, ToResolvedValue, ToShmem,
+)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
 #[repr(u8)]
 #[allow(missing_docs)]
 pub enum GenericFontFamily {
@@ -373,6 +377,35 @@ impl SingleFontFamily {
         }))
     }
 
+    #[cfg(feature = "servo")]
+    /// Get the corresponding font-family with Atom
+    pub fn from_atom(input: Atom) -> SingleFontFamily {
+        match input {
+            atom!("serif") => return SingleFontFamily::Generic(GenericFontFamily::Serif),
+            atom!("sans-serif") => return SingleFontFamily::Generic(GenericFontFamily::SansSerif),
+            atom!("cursive") => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
+            atom!("fantasy") => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
+            atom!("monospace") => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            _ => {},
+        }
+
+        match_ignore_ascii_case! { &input,
+            "serif" => return SingleFontFamily::Generic(GenericFontFamily::Serif),
+            "sans-serif" => return SingleFontFamily::Generic(GenericFontFamily::SansSerif),
+            "cursive" => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
+            "fantasy" => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
+            "monospace" => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            _ => {}
+        }
+
+        // We don't know if it's quoted or not. So we set it to
+        // quoted by default.
+        SingleFontFamily::FamilyName(FamilyName {
+            name: input,
+            syntax: FontFamilyNameSyntax::Quoted,
+        })
+    }
+
     #[cfg(feature = "gecko")]
     /// Get the corresponding font-family with family name
     fn from_font_family_name(family: &structs::FontFamilyName) -> SingleFontFamily {
@@ -389,7 +422,7 @@ impl SingleFontFamily {
 }
 
 #[cfg(feature = "servo")]
-#[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToResolvedValue)]
+#[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToResolvedValue, ToShmem)]
 /// A list of SingleFontFamily
 pub struct FontFamilyList(Box<[SingleFontFamily]>);
 
@@ -501,7 +534,7 @@ impl FontFamilyList {
         let mut iter = self.iter();
         if let Some(SingleFontFamily::Generic(f)) = iter.next() {
             if iter.next().is_none() {
-                return Some(f);
+                return Some(f.clone());
             }
         }
         None
diff --git a/components/style/values/generics/grid.rs b/components/style/values/generics/grid.rs
index 393e570f066..d20ba265ab2 100644
--- a/components/style/values/generics/grid.rs
+++ b/components/style/values/generics/grid.rs
@@ -557,7 +557,7 @@ pub enum TrackListType {
 /// A grid `<track-list>` type.
 ///
 /// <https://drafts.csswg.org/css-grid/#typedef-track-list>
-#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToShmem, ToResolvedValue)]
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToResolvedValue, ToShmem)]
 pub struct TrackList<LengthPercentage, Integer> {
     /// The type of this `<track-list>` (auto, explicit or general).
     ///
diff --git a/components/style/values/generics/image.rs b/components/style/values/generics/image.rs
index a7fa6da9337..71d6a1b3849 100644
--- a/components/style/values/generics/image.rs
+++ b/components/style/values/generics/image.rs
@@ -157,7 +157,7 @@ pub struct ColorStop<Color, LengthPercentage> {
 /// Specified values for a paint worklet.
 /// <https://drafts.css-houdini.org/css-paint-api/>
 #[cfg_attr(feature = "servo", derive(MallocSizeOf))]
-#[derive(Clone, Debug, PartialEq, ToComputedValue)]
+#[derive(Clone, Debug, PartialEq, ToComputedValue, ToResolvedValue, ToShmem)]
 pub struct PaintWorklet {
     /// The name the worklet was registered with.
     pub name: Atom,
diff --git a/components/style/values/resolved/mod.rs b/components/style/values/resolved/mod.rs
index 7877ed71a0b..4003060148c 100644
--- a/components/style/values/resolved/mod.rs
+++ b/components/style/values/resolved/mod.rs
@@ -65,15 +65,16 @@ trivial_to_resolved_value!(u8);
 trivial_to_resolved_value!(i8);
 trivial_to_resolved_value!(u16);
 trivial_to_resolved_value!(u32);
-#[cfg(feature = "servo")]
-trivial_to_resolved_value!(Prefix);
 trivial_to_resolved_value!(String);
 trivial_to_resolved_value!(Box<str>);
 trivial_to_resolved_value!(cssparser::RGBA);
 trivial_to_resolved_value!(crate::Atom);
 trivial_to_resolved_value!(app_units::Au);
 trivial_to_resolved_value!(computed::url::ComputedUrl);
+#[cfg(feature = "gecko")]
 trivial_to_resolved_value!(computed::url::ComputedImageUrl);
+#[cfg(feature = "servo")]
+trivial_to_resolved_value!(html5ever::Prefix);
 
 impl<A, B> ToResolvedValue for (A, B)
 where
diff --git a/components/style/values/specified/font.rs b/components/style/values/specified/font.rs
index f02d44124a2..127b1bfc2fb 100644
--- a/components/style/values/specified/font.rs
+++ b/components/style/values/specified/font.rs
@@ -1192,7 +1192,7 @@ macro_rules! impl_variant_east_asian {
         )+
     } => {
         bitflags! {
-            #[derive(MallocSizeOf, ToShmem, ToResolvedValue)]
+            #[derive(MallocSizeOf, ToResolvedValue, ToShmem)]
             /// Vairants for east asian variant
             pub struct VariantEastAsian: u16 {
                 /// None of the features
diff --git a/components/to_shmem/Cargo.toml b/components/to_shmem/Cargo.toml
index bebc45e821d..2e7b06eaaca 100644
--- a/components/to_shmem/Cargo.toml
+++ b/components/to_shmem/Cargo.toml
@@ -10,13 +10,14 @@ name = "to_shmem"
 path = "lib.rs"
 
 [features]
-servo = ["serde", "cssparser/serde"]
+servo = ["serde", "cssparser/serde", "string_cache"]
 gecko = []
 
 [dependencies]
 cssparser = "0.25"
-serde = {version = "1.0", optional = true}
+serde = { version = "1.0", optional = true }
 servo_arc = { path = "../servo_arc" }
 smallbitvec = "2.1.1"
 smallvec = "0.6.6"
+string_cache = { version = "0.7", optional = true }
 thin-slice = "0.1.0"
diff --git a/components/to_shmem/lib.rs b/components/to_shmem/lib.rs
index 59fc2afb546..96dfbb3a5e9 100644
--- a/components/to_shmem/lib.rs
+++ b/components/to_shmem/lib.rs
@@ -16,6 +16,8 @@ extern crate cssparser;
 extern crate servo_arc;
 extern crate smallbitvec;
 extern crate smallvec;
+#[cfg(feature = "string_cache")]
+extern crate string_cache;
 extern crate thin_slice;
 
 use servo_arc::{Arc, ThinArc};
@@ -193,16 +195,18 @@ pub trait ToShmem: Sized {
 
 #[macro_export]
 macro_rules! impl_trivial_to_shmem {
-    ($($ty:ty),*) => {$(
-        impl $crate::ToShmem for $ty {
-            fn to_shmem(
-                &self,
-                _builder: &mut $crate::SharedMemoryBuilder,
-            ) -> ::std::mem::ManuallyDrop<Self> {
-                ::std::mem::ManuallyDrop::new(*self)
+    ($($ty:ty),*) => {
+        $(
+            impl $crate::ToShmem for $ty {
+                fn to_shmem(
+                    &self,
+                    _builder: &mut $crate::SharedMemoryBuilder,
+                ) -> ::std::mem::ManuallyDrop<Self> {
+                    ::std::mem::ManuallyDrop::new(*self)
+                }
             }
-        }
-    )*};
+        )*
+    };
 }
 
 impl_trivial_to_shmem!(
@@ -522,3 +526,17 @@ impl ToShmem for SmallBitVec {
         ManuallyDrop::new(unsafe { SmallBitVec::from_storage(storage) })
     }
 }
+
+#[cfg(feature = "string_cache")]
+impl<Static: string_cache::StaticAtomSet> ToShmem for string_cache::Atom<Static> {
+    fn to_shmem(&self, _: &mut SharedMemoryBuilder) -> ManuallyDrop<Self> {
+        // NOTE(emilio): In practice, this can be implemented trivially if
+        // string_cache could expose the implementation detail of static atoms
+        // being an index into the static table (and panicking in the
+        // non-static, non-inline cases).
+        unimplemented!(
+            "If servo wants to share stylesheets across processes, \
+             then ToShmem for Atom needs to be implemented"
+        )
+    }
+}
diff --git a/components/to_shmem_derive/to_shmem.rs b/components/to_shmem_derive/to_shmem.rs
index 1335ef4eea6..e7ff8c29b8c 100644
--- a/components/to_shmem_derive/to_shmem.rs
+++ b/components/to_shmem_derive/to_shmem.rs
@@ -40,7 +40,7 @@ pub fn derive(mut input: syn::DeriveInput) -> TokenStream {
 
     quote! {
         impl #impl_generics ::to_shmem::ToShmem for #name #ty_generics #where_clause {
-            #[allow(unused_variables)]
+            #[allow(unused_variables, unreachable_code)]
             fn to_shmem(
                 &self,
                 builder: &mut ::to_shmem::SharedMemoryBuilder,
diff --git a/components/url/Cargo.toml b/components/url/Cargo.toml
index dbbed4f58db..1a59812e071 100644
--- a/components/url/Cargo.toml
+++ b/components/url/Cargo.toml
@@ -13,6 +13,8 @@ path = "lib.rs"
 [dependencies]
 malloc_size_of = { path = "../malloc_size_of", features = ["servo"] }
 malloc_size_of_derive = "0.1"
+to_shmem = { path = "../to_shmem" }
+to_shmem_derive = { path = "../to_shmem_derive" }
 serde = {version = "1.0", features = ["derive"]}
 servo_rand = {path = "../rand"}
 url = "1.2"
diff --git a/components/url/lib.rs b/components/url/lib.rs
index dccd27a8b00..bb7c1fa4e35 100644
--- a/components/url/lib.rs
+++ b/components/url/lib.rs
@@ -20,10 +20,12 @@ pub use crate::origin::{ImmutableOrigin, MutableOrigin, OpaqueOrigin};
 use std::collections::hash_map::DefaultHasher;
 use std::fmt;
 use std::hash::Hasher;
+use std::mem::ManuallyDrop;
 use std::net::IpAddr;
 use std::ops::{Index, Range, RangeFrom, RangeFull, RangeTo};
 use std::path::Path;
 use std::sync::Arc;
+use to_shmem::{SharedMemoryBuilder, ToShmem};
 use url::{Position, Url};
 
 pub use url::Host;
@@ -31,6 +33,12 @@ pub use url::Host;
 #[derive(Clone, Eq, Hash, MallocSizeOf, Ord, PartialEq, PartialOrd)]
 pub struct ServoUrl(#[ignore_malloc_size_of = "Arc"] Arc<Url>);
 
+impl ToShmem for ServoUrl {
+    fn to_shmem(&self, _builder: &mut SharedMemoryBuilder) -> ManuallyDrop<Self> {
+        unimplemented!("If servo wants to share stylesheets across processes, ToShmem for Url must be implemented")
+    }
+}
+
 impl ServoUrl {
     pub fn from_url(url: Url) -> Self {
         ServoUrl(Arc::new(url))