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diff --git a/servo/components/style/gecko/url.rs b/servo/components/style/gecko/url.rs
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+++ b/servo/components/style/gecko/url.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Common handling for the specified value CSS url() values.
+
+use crate::gecko_bindings::bindings;
+use crate::gecko_bindings::structs;
+use crate::parser::{Parse, ParserContext};
+use crate::stylesheets::{CorsMode, UrlExtraData};
+use crate::values::computed::{Context, ToComputedValue};
+use cssparser::Parser;
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use nsstring::nsCString;
+use servo_arc::Arc;
+use std::collections::HashMap;
+use std::fmt::{self, Write};
+use std::mem::ManuallyDrop;
+use std::sync::RwLock;
+use style_traits::{CssWriter, ParseError, ToCss};
+use to_shmem::{self, SharedMemoryBuilder, ToShmem};
+
+/// A CSS url() value for gecko.
+#[derive(Clone, Debug, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+#[css(function = "url")]
+#[repr(C)]
+pub struct CssUrl(pub Arc<CssUrlData>);
+
+/// Data shared between CssUrls.
+///
+/// cbindgen:derive-eq=false
+/// cbindgen:derive-neq=false
+#[derive(Debug, SpecifiedValueInfo, ToCss, ToShmem)]
+#[repr(C)]
+pub struct CssUrlData {
+    /// The URL in unresolved string form.
+    serialization: crate::OwnedStr,
+
+    /// The URL extra data.
+    #[css(skip)]
+    pub extra_data: UrlExtraData,
+
+    /// The CORS mode that will be used for the load.
+    #[css(skip)]
+    cors_mode: CorsMode,
+
+    /// Data to trigger a load from Gecko. This is mutable in C++.
+    ///
+    /// TODO(emilio): Maybe we can eagerly resolve URLs and make this immutable?
+    #[css(skip)]
+    load_data: LoadDataSource,
+}
+
+impl PartialEq for CssUrlData {
+    fn eq(&self, other: &Self) -> bool {
+        self.serialization == other.serialization &&
+            self.extra_data == other.extra_data &&
+            self.cors_mode == other.cors_mode
+    }
+}
+
+impl CssUrl {
+    fn parse_with_cors_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+    ) -> Result<Self, ParseError<'i>> {
+        let url = input.expect_url()?;
+        Ok(Self::parse_from_string(
+            url.as_ref().to_owned(),
+            context,
+            cors_mode,
+        ))
+    }
+
+    /// Parse a URL from a string value that is a valid CSS token for a URL.
+    pub fn parse_from_string(url: String, context: &ParserContext, cors_mode: CorsMode) -> Self {
+        CssUrl(Arc::new(CssUrlData {
+            serialization: url.into(),
+            extra_data: context.url_data.clone(),
+            cors_mode,
+            load_data: LoadDataSource::Owned(LoadData::default()),
+        }))
+    }
+
+    /// Returns true if the URL is definitely invalid. We don't eagerly resolve
+    /// URLs in gecko, so we just return false here.
+    /// use its |resolved| status.
+    pub fn is_invalid(&self) -> bool {
+        false
+    }
+
+    /// Returns true if this URL looks like a fragment.
+    /// See https://drafts.csswg.org/css-values/#local-urls
+    #[inline]
+    pub fn is_fragment(&self) -> bool {
+        self.0.is_fragment()
+    }
+
+    /// Return the unresolved url as string, or the empty string if it's
+    /// invalid.
+    #[inline]
+    pub fn as_str(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+impl CssUrlData {
+    /// Returns true if this URL looks like a fragment.
+    /// See https://drafts.csswg.org/css-values/#local-urls
+    pub fn is_fragment(&self) -> bool {
+        self.as_str()
+            .as_bytes()
+            .iter()
+            .next()
+            .map_or(false, |b| *b == b'#')
+    }
+
+    /// Return the unresolved url as string, or the empty string if it's
+    /// invalid.
+    pub fn as_str(&self) -> &str {
+        &*self.serialization
+    }
+}
+
+impl Parse for CssUrl {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_cors_mode(context, input, CorsMode::None)
+    }
+}
+
+impl Eq for CssUrl {}
+
+impl MallocSizeOf for CssUrl {
+    fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
+        // XXX: measure `serialization` once bug 1397971 lands
+
+        // We ignore `extra_data`, because RefPtr is tricky, and there aren't
+        // many of them in practise (sharing is common).
+
+        0
+    }
+}
+
+/// A key type for LOAD_DATA_TABLE.
+#[derive(Eq, Hash, PartialEq)]
+struct LoadDataKey(*const LoadDataSource);
+
+unsafe impl Sync for LoadDataKey {}
+unsafe impl Send for LoadDataKey {}
+
+bitflags! {
+    /// Various bits of mutable state that are kept for image loads.
+    #[repr(C)]
+    pub struct LoadDataFlags: u8 {
+        /// Whether we tried to resolve the uri at least once.
+        const TRIED_TO_RESOLVE_URI = 1 << 0;
+        /// Whether we tried to resolve the image at least once.
+        const TRIED_TO_RESOLVE_IMAGE = 1 << 1;
+    }
+}
+
+/// This is usable and movable from multiple threads just fine, as long as it's
+/// not cloned (it is not clonable), and the methods that mutate it run only on
+/// the main thread (when all the other threads we care about are paused).
+unsafe impl Sync for LoadData {}
+unsafe impl Send for LoadData {}
+
+/// The load data for a given URL. This is mutable from C++, and shouldn't be
+/// accessed from rust for anything.
+#[repr(C)]
+#[derive(Debug)]
+pub struct LoadData {
+    /// A strong reference to the imgRequestProxy, if any, that should be
+    /// released on drop.
+    ///
+    /// These are raw pointers because they are not safe to reference-count off
+    /// the main thread.
+    resolved_image: *mut structs::imgRequestProxy,
+    /// A strong reference to the resolved URI of this image.
+    resolved_uri: *mut structs::nsIURI,
+    /// A few flags that are set when resolving the image or such.
+    flags: LoadDataFlags,
+}
+
+impl Drop for LoadData {
+    fn drop(&mut self) {
+        unsafe { bindings::Gecko_LoadData_Drop(self) }
+    }
+}
+
+impl Default for LoadData {
+    fn default() -> Self {
+        Self {
+            resolved_image: std::ptr::null_mut(),
+            resolved_uri: std::ptr::null_mut(),
+            flags: LoadDataFlags::empty(),
+        }
+    }
+}
+
+/// The data for a load, or a lazy-loaded, static member that will be stored in
+/// LOAD_DATA_TABLE, keyed by the memory location of this object, which is
+/// always in the heap because it's inside the CssUrlData object.
+///
+/// This type is meant not to be used from C++ so we don't derive helper
+/// methods.
+///
+/// cbindgen:derive-helper-methods=false
+#[derive(Debug)]
+#[repr(u8, C)]
+pub enum LoadDataSource {
+    /// An owned copy of the load data.
+    Owned(LoadData),
+    /// A lazily-resolved copy of it.
+    Lazy,
+}
+
+impl LoadDataSource {
+    /// Gets the load data associated with the source.
+    ///
+    /// This relies on the source on being in a stable location if lazy.
+    #[inline]
+    pub unsafe fn get(&self) -> *const LoadData {
+        match *self {
+            LoadDataSource::Owned(ref d) => return d,
+            LoadDataSource::Lazy => {},
+        }
+
+        let key = LoadDataKey(self);
+
+        {
+            let guard = LOAD_DATA_TABLE.read().unwrap();
+            if let Some(r) = guard.get(&key) {
+                return &**r;
+            }
+        }
+        let mut guard = LOAD_DATA_TABLE.write().unwrap();
+        let r = guard.entry(key).or_insert_with(Default::default);
+        &**r
+    }
+}
+
+impl ToShmem for LoadDataSource {
+    fn to_shmem(&self, _builder: &mut SharedMemoryBuilder) -> to_shmem::Result<Self> {
+        Ok(ManuallyDrop::new(match self {
+            LoadDataSource::Owned(..) => LoadDataSource::Lazy,
+            LoadDataSource::Lazy => LoadDataSource::Lazy,
+        }))
+    }
+}
+
+/// A specified non-image `url()` value.
+pub type SpecifiedUrl = CssUrl;
+
+/// Clears LOAD_DATA_TABLE.  Entries in this table, which are for specified URL
+/// values that come from shared memory style sheets, would otherwise persist
+/// until the end of the process and be reported as leaks.
+pub fn shutdown() {
+    LOAD_DATA_TABLE.write().unwrap().clear();
+}
+
+impl ToComputedValue for SpecifiedUrl {
+    type ComputedValue = ComputedUrl;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        ComputedUrl(self.clone())
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        computed.0.clone()
+    }
+}
+
+/// A specified image `url()` value.
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct SpecifiedImageUrl(pub SpecifiedUrl);
+
+impl SpecifiedImageUrl {
+    /// Parse a URL from a string value that is a valid CSS token for a URL.
+    pub fn parse_from_string(url: String, context: &ParserContext, cors_mode: CorsMode) -> Self {
+        SpecifiedImageUrl(SpecifiedUrl::parse_from_string(url, context, cors_mode))
+    }
+
+    /// Provides an alternate method for parsing that associates the URL
+    /// with anonymous CORS headers.
+    pub fn parse_with_cors_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(SpecifiedImageUrl(SpecifiedUrl::parse_with_cors_mode(
+            context, input, cors_mode,
+        )?))
+    }
+}
+
+impl Parse for SpecifiedImageUrl {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        SpecifiedUrl::parse(context, input).map(SpecifiedImageUrl)
+    }
+}
+
+impl ToComputedValue for SpecifiedImageUrl {
+    type ComputedValue = ComputedImageUrl;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        ComputedImageUrl(self.0.to_computed_value(context))
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        SpecifiedImageUrl(ToComputedValue::from_computed_value(&computed.0))
+    }
+}
+
+/// The computed value of a CSS non-image `url()`.
+///
+/// The only difference between specified and computed URLs is the
+/// serialization.
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq)]
+#[repr(C)]
+pub struct ComputedUrl(pub SpecifiedUrl);
+
+impl ComputedUrl {
+    fn serialize_with<W>(
+        &self,
+        function: unsafe extern "C" fn(*const Self, *mut nsCString),
+        dest: &mut CssWriter<W>,
+    ) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("url(")?;
+        unsafe {
+            let mut string = nsCString::new();
+            function(self, &mut string);
+            string.as_str_unchecked().to_css(dest)?;
+        }
+        dest.write_char(')')
+    }
+}
+
+impl ToCss for ComputedUrl {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.serialize_with(bindings::Gecko_GetComputedURLSpec, dest)
+    }
+}
+
+/// The computed value of a CSS image `url()`.
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq)]
+#[repr(transparent)]
+pub struct ComputedImageUrl(pub ComputedUrl);
+
+impl ToCss for ComputedImageUrl {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0
+            .serialize_with(bindings::Gecko_GetComputedImageURLSpec, dest)
+    }
+}
+
+lazy_static! {
+    /// A table mapping CssUrlData objects to their lazily created LoadData
+    /// objects.
+    static ref LOAD_DATA_TABLE: RwLock<HashMap<LoadDataKey, Box<LoadData>>> = {
+        Default::default()
+    };
+}