style: Avoid cloning all over the error reporter.

components/layout_thread/lib.rs

@@ -110,7 +110,7 @@ use style::animation::Animation;
 use style::context::{QuirksMode, ReflowGoal, SharedStyleContext, ThreadLocalStyleContextCreationInfo};
 use style::data::StoredRestyleHint;
 use style::dom::{ShowSubtree, ShowSubtreeDataAndPrimaryValues, TElement, TNode};
-use style::error_reporting::{ParseErrorReporter, StdoutErrorReporter};
+use style::error_reporting::StdoutErrorReporter;
 use style::logical_geometry::LogicalPoint;
 use style::media_queries::{Device, MediaType};
 use style::parser::ParserContextExtraData;
@@ -505,7 +505,7 @@ impl LayoutThread {
                 stylist: rw_data.stylist.clone(),
                 running_animations: self.running_animations.clone(),
                 expired_animations: self.expired_animations.clone(),
-                error_reporter: self.error_reporter.clone(),
+                error_reporter: Box::new(self.error_reporter.clone()),
                 local_context_creation_data: Mutex::new(thread_local_style_context_creation_data),
                 timer: self.timer.clone(),
                 quirks_mode: self.quirks_mode.unwrap(),
@@ -1563,7 +1563,7 @@ fn get_ua_stylesheets() -> Result<UserAgentStylesheets, &'static str> {
             Origin::UserAgent,
             Default::default(),
             None,
-            Box::new(StdoutErrorReporter),
+            &StdoutErrorReporter,
             ParserContextExtraData::default()))
     }
 
@@ -1576,8 +1576,7 @@ fn get_ua_stylesheets() -> Result<UserAgentStylesheets, &'static str> {
     for &(ref contents, ref url) in &opts::get().user_stylesheets {
         user_or_user_agent_stylesheets.push(Stylesheet::from_bytes(
             &contents, url.clone(), None, None, Origin::User, Default::default(),
-            None, Box::new(StdoutErrorReporter),
+            None, &StdoutErrorReporter, ParserContextExtraData::default()));
-            ParserContextExtraData::default()));
     }
 
     let quirks_mode_stylesheet = try!(parse_ua_stylesheet("quirks-mode.css"));

components/script/dom/css.rs

@@ -29,7 +29,7 @@ impl CSS {
     pub fn Supports(win: &Window, property: DOMString, value: DOMString) -> bool {
         let decl = Declaration { prop: property.into(), val: value.into() };
         let url = win.Document().url();
-        let context = ParserContext::new_for_cssom(&url);
+        let context = ParserContext::new_for_cssom(&url, win.css_error_reporter());
         decl.eval(&context)
     }
 
@@ -39,7 +39,7 @@ impl CSS {
         let cond = parse_condition_or_declaration(&mut input);
         if let Ok(cond) = cond {
             let url = win.Document().url();
-            let context = ParserContext::new_for_cssom(&url);
+            let context = ParserContext::new_for_cssom(&url, win.css_error_reporter());
             cond.eval(&context)
         } else {
             false

components/script/dom/csssupportsrule.rs

@@ -56,8 +56,10 @@ impl CSSSupportsRule {
         let mut input = Parser::new(&text);
         let cond = SupportsCondition::parse(&mut input);
         if let Ok(cond) = cond {
-            let url = self.global().as_window().Document().url();
+            let global = self.global();
-            let context = ParserContext::new_for_cssom(&url);
+            let win = global.as_window();
+            let url = win.Document().url();
+            let context = ParserContext::new_for_cssom(&url, win.css_error_reporter());
             let enabled = cond.eval(&context);
             let mut rule = self.supportsrule.write();
             rule.condition = cond;

components/script/dom/window.rs

@@ -331,8 +331,8 @@ impl Window {
          &self.bluetooth_extra_permission_data
     }
 
-    pub fn css_error_reporter(&self) -> Box<ParseErrorReporter + Send> {
+    pub fn css_error_reporter(&self) -> &ParseErrorReporter {
-        self.error_reporter.clone()
+        &self.error_reporter
     }
 
     /// Sets a new list of scroll offsets.

components/script_layout_interface/reporter.rs

@@ -11,7 +11,7 @@ use servo_url::ServoUrl;
 use std::sync::{Mutex, Arc};
 use style::error_reporting::ParseErrorReporter;
 
-#[derive(HeapSizeOf)]
+#[derive(HeapSizeOf, Clone)]
 pub struct CSSErrorReporter {
     pub pipelineid: PipelineId,
     // Arc+Mutex combo is necessary to make this struct Sync,
@@ -22,11 +22,18 @@ pub struct CSSErrorReporter {
 }
 
 impl ParseErrorReporter for CSSErrorReporter {
-     fn report_error(&self, input: &mut Parser, position: SourcePosition, message: &str,
+     fn report_error(&self,
+                     input: &mut Parser,
+                     position: SourcePosition,
+                     message: &str,
                      url: &ServoUrl) {
         let location = input.source_location(position);
         if log_enabled!(log::LogLevel::Info) {
-             info!("Url:\t{}\n{}:{} {}", url.as_str(), location.line, location.column, message)
+             info!("Url:\t{}\n{}:{} {}",
+                   url.as_str(),
+                   location.line,
+                   location.column,
+                   message)
         }
 
          //TODO: report a real filename
@@ -37,11 +44,4 @@ impl ParseErrorReporter for CSSErrorReporter {
                                                      location.column,
                                                      message.to_owned()));
      }
-
-     fn clone(&self) -> Box<ParseErrorReporter + Send + Sync> {
-         box CSSErrorReporter {
-             pipelineid: self.pipelineid,
-             script_chan: self.script_chan.clone(),
-         }
-     }
 }

components/style/animation.rs

@@ -432,7 +432,7 @@ fn compute_style_for_animation_step(context: &SharedStyleContext,
                                                previous_style,
                                                previous_style,
                                                /* cascade_info = */ None,
-                                               context.error_reporter.clone(),
+                                               &*context.error_reporter,
                                                /* Metrics provider */ None,
                                                CascadeFlags::empty());
             computed

components/style/context.rs

@@ -72,7 +72,7 @@ pub struct SharedStyleContext {
     pub expired_animations: Arc<RwLock<HashMap<OpaqueNode, Vec<Animation>>>>,
 
     ///The CSS error reporter for all CSS loaded in this layout thread
-    pub error_reporter: Box<ParseErrorReporter + Sync>,
+    pub error_reporter: Box<ParseErrorReporter>,
 
     /// Data needed to create the thread-local style context from the shared one.
     pub local_context_creation_data: Mutex<ThreadLocalStyleContextCreationInfo>,

components/style/error_reporting.rs

@@ -11,16 +11,16 @@ use log;
 use servo_url::ServoUrl;
 
 /// A generic trait for an error reporter.
-pub trait ParseErrorReporter {
+pub trait ParseErrorReporter : Sync + Send {
     /// Called the style engine detects an error.
     ///
     /// Returns the current input being parsed, the source position it was
     /// reported from, and a message.
-    fn report_error(&self, input: &mut Parser, position: SourcePosition, message: &str, url: &ServoUrl);
+    fn report_error(&self,
-    /// Clone this error reporter.
+                    input: &mut Parser,
-    ///
+                    position: SourcePosition,
-    /// TODO(emilio): I'm pretty sure all the box shenanigans can go away.
+                    message: &str,
-    fn clone(&self) -> Box<ParseErrorReporter + Send + Sync>;
+                    url: &ServoUrl);
 }
 
 /// An error reporter that reports the errors to the `info` log channel.
@@ -28,15 +28,14 @@ pub trait ParseErrorReporter {
 /// TODO(emilio): The name of this reporter is a lie, and should be renamed!
 pub struct StdoutErrorReporter;
 impl ParseErrorReporter for StdoutErrorReporter {
-    fn report_error(&self, input: &mut Parser, position: SourcePosition, message: &str,
+    fn report_error(&self,
+                    input: &mut Parser,
+                    position: SourcePosition,
+                    message: &str,
                     url: &ServoUrl) {
         if log_enabled!(log::LogLevel::Info) {
             let location = input.source_location(position);
             info!("Url:\t{}\n{}:{} {}", url.as_str(), location.line, location.column, message)
         }
     }
-
-    fn clone(&self) -> Box<ParseErrorReporter + Send + Sync> {
-        Box::new(StdoutErrorReporter)
-    }
 }

components/style/gecko/wrapper.rs

@@ -299,7 +299,7 @@ impl<'le> GeckoElement<'le> {
     pub fn parse_style_attribute(value: &str,
                                  base_url: &ServoUrl,
                                  extra_data: ParserContextExtraData) -> PropertyDeclarationBlock {
-        parse_style_attribute(value, base_url, Box::new(StdoutErrorReporter), extra_data)
+        parse_style_attribute(value, base_url, &StdoutErrorReporter, extra_data)
     }
 
     fn flags(&self) -> u32 {

components/style/keyframes.rs

@@ -126,10 +126,10 @@ impl Keyframe {
                  parent_stylesheet: &Stylesheet,
                  extra_data: ParserContextExtraData)
                  -> Result<Arc<RwLock<Self>>, ()> {
-        let error_reporter = Box::new(MemoryHoleReporter);
+        let error_reporter = MemoryHoleReporter;
         let context = ParserContext::new_with_extra_data(parent_stylesheet.origin,
                                                          &parent_stylesheet.base_url,
-                                                         error_reporter,
+                                                         &error_reporter,
                                                          extra_data);
         let mut input = Parser::new(css);
 

components/style/matching.rs

@@ -544,7 +544,7 @@ trait PrivateMatchMethods: TElement {
                              inherited_values,
                              layout_parent_style,
                              Some(&mut cascade_info),
-                             shared_context.error_reporter.clone(),
+                             &*shared_context.error_reporter,
                              cascade_flags));
 
         cascade_info.finish(&self.as_node());

components/style/parser.rs

@@ -12,7 +12,7 @@ use error_reporting::ParseErrorReporter;
 use gecko_bindings::sugar::refptr::{GeckoArcPrincipal, GeckoArcURI};
 use servo_url::ServoUrl;
 use style_traits::OneOrMoreCommaSeparated;
-use stylesheets::{MemoryHoleReporter, Origin};
+use stylesheets::Origin;
 
 /// Extra data that the style backend may need to parse stylesheets.
 #[cfg(not(feature = "gecko"))]
@@ -67,7 +67,7 @@ pub struct ParserContext<'a> {
     /// The base url we're parsing this stylesheet as.
     pub base_url: &'a ServoUrl,
     /// An error reporter to report syntax errors.
-    pub error_reporter: Box<ParseErrorReporter + Send>,
+    pub error_reporter: &'a ParseErrorReporter,
     /// Implementation-dependent extra data.
     pub extra_data: ParserContextExtraData,
 }
@@ -76,7 +76,7 @@ impl<'a> ParserContext<'a> {
     /// Create a `ParserContext` with extra data.
     pub fn new_with_extra_data(stylesheet_origin: Origin,
                                base_url: &'a ServoUrl,
-                               error_reporter: Box<ParseErrorReporter + Send>,
+                               error_reporter: &'a ParseErrorReporter,
                                extra_data: ParserContextExtraData)
                                -> ParserContext<'a> {
         ParserContext {
@@ -90,22 +90,27 @@ impl<'a> ParserContext<'a> {
     /// Create a parser context with the default extra data.
     pub fn new(stylesheet_origin: Origin,
                base_url: &'a ServoUrl,
-               error_reporter: Box<ParseErrorReporter + Send>)
+               error_reporter: &'a ParseErrorReporter)
                -> ParserContext<'a> {
         let extra_data = ParserContextExtraData::default();
         Self::new_with_extra_data(stylesheet_origin, base_url, error_reporter, extra_data)
     }
 
     /// Create a parser context for on-the-fly parsing in CSSOM
-    pub fn new_for_cssom(base_url: &'a ServoUrl) -> ParserContext<'a> {
+    pub fn new_for_cssom(base_url: &'a ServoUrl,
-        Self::new(Origin::User, base_url, Box::new(MemoryHoleReporter))
+                         error_reporter: &'a ParseErrorReporter)
+                         -> ParserContext<'a> {
+        Self::new(Origin::User, base_url, error_reporter)
     }
 }
 
 /// Defaults to a no-op.
 /// Set a `RUST_LOG=style::errors` environment variable
 /// to log CSS parse errors to stderr.
-pub fn log_css_error(input: &mut Parser, position: SourcePosition, message: &str, parsercontext: &ParserContext) {
+pub fn log_css_error(input: &mut Parser,
+                     position: SourcePosition,
+                     message: &str,
+                     parsercontext: &ParserContext) {
     let servo_url = parsercontext.base_url;
     parsercontext.error_reporter.report_error(input, position, message, servo_url);
 }

components/style/properties/declaration_block.rs

@@ -11,7 +11,6 @@ use cssparser::{Parser, AtRuleParser, DeclarationParser, Delimiter};
 use error_reporting::ParseErrorReporter;
 use parser::{ParserContext, ParserContextExtraData, log_css_error};
 use servo_url::ServoUrl;
-use std::boxed::Box as StdBox;
 use std::fmt;
 use style_traits::ToCss;
 use stylesheets::Origin;
@@ -570,10 +569,13 @@ pub fn append_serialization<'a, W, I, N>(dest: &mut W,
 /// shared between Servo and Gecko.
 pub fn parse_style_attribute(input: &str,
                              base_url: &ServoUrl,
-                             error_reporter: StdBox<ParseErrorReporter + Send>,
+                             error_reporter: &ParseErrorReporter,
                              extra_data: ParserContextExtraData)
                              -> PropertyDeclarationBlock {
-    let context = ParserContext::new_with_extra_data(Origin::Author, base_url, error_reporter, extra_data);
+    let context = ParserContext::new_with_extra_data(Origin::Author,
+                                                     base_url,
+                                                     error_reporter,
+                                                     extra_data);
     parse_property_declaration_list(&context, &mut Parser::new(input))
 }
 
@@ -585,10 +587,13 @@ pub fn parse_style_attribute(input: &str,
 pub fn parse_one_declaration(id: PropertyId,
                              input: &str,
                              base_url: &ServoUrl,
-                             error_reporter: StdBox<ParseErrorReporter + Send>,
+                             error_reporter: &ParseErrorReporter,
                              extra_data: ParserContextExtraData)
                              -> Result<ParsedDeclaration, ()> {
-    let context = ParserContext::new_with_extra_data(Origin::Author, base_url, error_reporter, extra_data);
+    let context = ParserContext::new_with_extra_data(Origin::Author,
+                                                     base_url,
+                                                     error_reporter,
+                                                     extra_data);
     Parser::new(input).parse_entirely(|parser| {
         ParsedDeclaration::parse(id, &context, parser, false)
             .map_err(|_| ())

components/style/properties/helpers.mako.rs

@@ -233,7 +233,7 @@
                                 context: &mut computed::Context,
                                 cacheable: &mut bool,
                                 cascade_info: &mut Option<<&mut CascadeInfo>,
-                                error_reporter: &mut StdBox<ParseErrorReporter + Send>) {
+                                error_reporter: &ParseErrorReporter) {
             let declared_value = match *declaration {
                 PropertyDeclaration::${property.camel_case}(ref declared_value) => {
                     declared_value

components/style/properties/longhand/box.mako.rs

@@ -85,7 +85,7 @@
                                    _inherited_style: &ComputedValues,
                                    context: &mut computed::Context,
                                    _cacheable: &mut bool,
-                                   _error_reporter: &mut StdBox<ParseErrorReporter + Send>) {
+                                   _error_reporter: &ParseErrorReporter) {
             longhands::_servo_display_for_hypothetical_box::derive_from_display(context);
             longhands::_servo_text_decorations_in_effect::derive_from_display(context);
             longhands::_servo_under_display_none::derive_from_display(context);

components/style/properties/longhand/text.mako.rs

@@ -210,7 +210,7 @@ ${helpers.single_keyword("unicode-bidi",
                                    _inherited_style: &ComputedValues,
                                    context: &mut computed::Context,
                                    _cacheable: &mut bool,
-                                   _error_reporter: &mut StdBox<ParseErrorReporter + Send>) {
+                                   _error_reporter: &ParseErrorReporter) {
                 longhands::_servo_text_decorations_in_effect::derive_from_text_decoration(context);
         }
     % endif

components/style/properties/properties.mako.rs

@@ -11,7 +11,6 @@
 <%namespace name="helpers" file="/helpers.mako.rs" />
 
 use std::borrow::Cow;
-use std::boxed::Box as StdBox;
 use std::collections::HashSet;
 use std::fmt;
 use std::sync::Arc;
@@ -288,7 +287,7 @@ impl PropertyDeclarationIdSet {
             % endif
             custom_properties: &Option<Arc<::custom_properties::ComputedValuesMap>>,
             f: F,
-            error_reporter: &mut StdBox<ParseErrorReporter + Send>)
+            error_reporter: &ParseErrorReporter)
             % if property.boxed:
                 where F: FnOnce(&DeclaredValue<Box<longhands::${property.ident}::SpecifiedValue>>)
             % else:
@@ -322,7 +321,7 @@ impl PropertyDeclarationIdSet {
                 from_shorthand: Option<ShorthandId>,
                 custom_properties: &Option<Arc<::custom_properties::ComputedValuesMap>>,
                 f: F,
-                error_reporter: &mut StdBox<ParseErrorReporter + Send>,
+                error_reporter: &ParseErrorReporter,
                 extra_data: ParserContextExtraData)
                 % if property.boxed:
                     where F: FnOnce(&DeclaredValue<Box<longhands::${property.ident}::SpecifiedValue>>)
@@ -338,7 +337,7 @@ impl PropertyDeclarationIdSet {
                     // FIXME(pcwalton): Cloning the error reporter is slow! But so are custom
                     // properties, so whatever...
                     let context = ParserContext::new_with_extra_data(
-                        ::stylesheets::Origin::Author, base_url, (*error_reporter).clone(),
+                        ::stylesheets::Origin::Author, base_url, error_reporter,
                         extra_data);
                     Parser::new(&css).parse_entirely(|input| {
                         match from_shorthand {
@@ -1764,7 +1763,7 @@ pub type CascadePropertyFn =
                      context: &mut computed::Context,
                      cacheable: &mut bool,
                      cascade_info: &mut Option<<&mut CascadeInfo>,
-                     error_reporter: &mut StdBox<ParseErrorReporter + Send>);
+                     error_reporter: &ParseErrorReporter);
 
 /// A per-longhand array of functions to perform the CSS cascade on each of
 /// them, effectively doing virtual dispatch.
@@ -1808,7 +1807,7 @@ pub fn cascade(device: &Device,
                parent_style: Option<<&ComputedValues>,
                layout_parent_style: Option<<&ComputedValues>,
                cascade_info: Option<<&mut CascadeInfo>,
-               error_reporter: StdBox<ParseErrorReporter + Send>,
+               error_reporter: &ParseErrorReporter,
                flags: CascadeFlags)
                -> ComputedValues {
     debug_assert_eq!(parent_style.is_some(), layout_parent_style.is_some());
@@ -1863,7 +1862,7 @@ pub fn apply_declarations<'a, F, I>(device: &Device,
                                     inherited_style: &ComputedValues,
                                     layout_parent_style: &ComputedValues,
                                     mut cascade_info: Option<<&mut CascadeInfo>,
-                                    mut error_reporter: StdBox<ParseErrorReporter + Send>,
+                                    error_reporter: &ParseErrorReporter,
                                     font_metrics_provider: Option<<&FontMetricsProvider>,
                                     flags: CascadeFlags)
                                     -> ComputedValues
@@ -1991,7 +1990,7 @@ pub fn apply_declarations<'a, F, I>(device: &Device,
                                              &mut context,
                                              &mut cacheable,
                                              &mut cascade_info,
-                                             &mut error_reporter);
+                                             error_reporter);
         }
         % if category_to_cascade_now == "early":
             let writing_mode = get_writing_mode(context.style.get_inheritedbox());

components/style/stylesheets.rs

@@ -255,9 +255,6 @@ impl ParseErrorReporter for MemoryHoleReporter {
             _: &ServoUrl) {
         // do nothing
     }
-    fn clone(&self) -> Box<ParseErrorReporter + Send + Sync> {
-        Box::new(MemoryHoleReporter)
-    }
 }
 
 #[allow(missing_docs)]
@@ -341,11 +338,11 @@ impl CssRule {
                  extra_data: ParserContextExtraData,
                  state: Option<State>)
                  -> Result<(Self, State), SingleRuleParseError> {
-        let error_reporter = Box::new(MemoryHoleReporter);
+        let error_reporter = MemoryHoleReporter;
         let mut namespaces = parent_stylesheet.namespaces.write();
         let context = ParserContext::new_with_extra_data(parent_stylesheet.origin,
                                                          &parent_stylesheet.base_url,
-                                                         error_reporter.clone(),
+                                                         &error_reporter,
                                                          extra_data);
         let mut input = Parser::new(css);
 
@@ -583,7 +580,7 @@ impl Stylesheet {
                       origin: Origin,
                       media: MediaList,
                       stylesheet_loader: Option<&StylesheetLoader>,
-                      error_reporter: Box<ParseErrorReporter + Send>,
+                      error_reporter: &ParseErrorReporter,
                       extra_data: ParserContextExtraData)
                       -> Stylesheet {
         let (string, _) = decode_stylesheet_bytes(
@@ -604,7 +601,7 @@ impl Stylesheet {
                              protocol_encoding_label: Option<&str>,
                              environment_encoding: Option<EncodingRef>,
                              stylesheet_loader: Option<&StylesheetLoader>,
-                             error_reporter: Box<ParseErrorReporter + Send>,
+                             error_reporter: &ParseErrorReporter,
                              extra_data: ParserContextExtraData) {
         let (string, _) = decode_stylesheet_bytes(
             bytes, protocol_encoding_label, environment_encoding);
@@ -619,7 +616,7 @@ impl Stylesheet {
     pub fn update_from_str(existing: &Stylesheet,
                            css: &str,
                            stylesheet_loader: Option<&StylesheetLoader>,
-                           error_reporter: Box<ParseErrorReporter + Send>,
+                           error_reporter: &ParseErrorReporter,
                            extra_data: ParserContextExtraData) {
         let mut rules = existing.rules.write();
         let mut namespaces = existing.namespaces.write();
@@ -668,7 +665,7 @@ impl Stylesheet {
                     origin: Origin,
                     media: MediaList,
                     stylesheet_loader: Option<&StylesheetLoader>,
-                    error_reporter: Box<ParseErrorReporter + Send>,
+                    error_reporter: &ParseErrorReporter,
                     extra_data: ParserContextExtraData) -> Stylesheet {
         let s = Stylesheet {
             origin: origin,

components/style/stylist.rs

@@ -329,7 +329,7 @@ impl Stylist {
                                 parent.map(|p| &**p),
                                 parent.map(|p| &**p),
                                 None,
-                                Box::new(StdoutErrorReporter),
+                                &StdoutErrorReporter,
                                 cascade_flags);
         ComputedStyle::new(rule_node, Arc::new(computed))
     }
@@ -411,7 +411,7 @@ impl Stylist {
                                 Some(&**parent),
                                 Some(&**parent),
                                 None,
-                                Box::new(StdoutErrorReporter),
+                                &StdoutErrorReporter,
                                 CascadeFlags::empty());
 
         // Apply the selector flags. We should be in sequential mode already,

ports/geckolib/glue.rs

@@ -166,6 +166,7 @@ fn create_shared_context(per_doc_data: &PerDocumentStyleDataImpl) -> SharedStyle
         stylist: per_doc_data.stylist.clone(),
         running_animations: per_doc_data.running_animations.clone(),
         expired_animations: per_doc_data.expired_animations.clone(),
+        // FIXME(emilio): Stop boxing here.
         error_reporter: Box::new(StdoutErrorReporter),
         local_context_creation_data: Mutex::new(local_context_data),
         timer: Timer::new(),
@@ -336,7 +337,7 @@ pub extern "C" fn Servo_StyleSheet_Empty(mode: SheetParsingMode) -> RawServoStyl
     };
     Arc::new(Stylesheet::from_str(
         "", url, origin, Default::default(), None,
-        Box::new(StdoutErrorReporter), extra_data)
+        &StdoutErrorReporter, extra_data)
     ).into_strong()
 }
 
@@ -379,7 +380,7 @@ pub extern "C" fn Servo_StyleSheet_FromUTF8Bytes(loader: *mut Loader,
 
     Arc::new(Stylesheet::from_str(
         input, url, origin, Default::default(), loader,
-        Box::new(StdoutErrorReporter), extra_data)
+        &StdoutErrorReporter, extra_data)
     ).into_strong()
 }
 
@@ -415,7 +416,7 @@ pub extern "C" fn Servo_StyleSheet_ClearAndUpdate(stylesheet: RawServoStyleSheet
     sheet.rules.write().0.clear();
 
     Stylesheet::update_from_str(&sheet, input, loader,
-                                Box::new(StdoutErrorReporter), extra_data);
+                                &StdoutErrorReporter, extra_data);
 }
 
 #[no_mangle]
@@ -746,9 +747,10 @@ pub extern "C" fn Servo_ParseProperty(property: *const nsACString, value: *const
 
     make_context!((base, data) => (base_url, extra_data));
 
+    let reporter = StdoutErrorReporter;
     let context = ParserContext::new_with_extra_data(Origin::Author,
                                                      &base_url,
-                                                     Box::new(StdoutErrorReporter),
+                                                     &reporter,
                                                      extra_data);
 
     match ParsedDeclaration::parse(id, &context, &mut Parser::new(value), false) {
@@ -874,7 +876,7 @@ fn set_property(declarations: RawServoDeclarationBlockBorrowed, property_id: Pro
 
     make_context!((base, data) => (base_url, extra_data));
     if let Ok(parsed) = parse_one_declaration(property_id, value, &base_url,
-                                              Box::new(StdoutErrorReporter), extra_data) {
+                                              &StdoutErrorReporter, extra_data) {
         let mut declarations = RwLock::<PropertyDeclarationBlock>::as_arc(&declarations).write();
         let importance = if is_important { Importance::Important } else { Importance::Normal };
         let mut changed = false;
@@ -1257,7 +1259,7 @@ pub extern "C" fn Servo_CSSSupports2(property: *const nsACString, value: *const
     let base_url = &*DUMMY_BASE_URL;
     let extra_data = ParserContextExtraData::default();
 
-    parse_one_declaration(id, &value, &base_url, Box::new(StdoutErrorReporter), extra_data).is_ok()
+    parse_one_declaration(id, &value, &base_url, &StdoutErrorReporter, extra_data).is_ok()
 }
 
 #[no_mangle]
@@ -1267,7 +1269,8 @@ pub extern "C" fn Servo_CSSSupports(cond: *const nsACString) -> bool {
     let cond = parse_condition_or_declaration(&mut input);
     if let Ok(cond) = cond {
         let url = ServoUrl::parse("about:blank").unwrap();
-        let context = ParserContext::new_for_cssom(&url);
+        let reporter = StdoutErrorReporter;
+        let context = ParserContext::new_for_cssom(&url, &reporter);
         cond.eval(&context)
     } else {
         false

tests/unit/style/media_queries.rs

@@ -21,10 +21,6 @@ impl ParseErrorReporter for CSSErrorReporterTest {
     fn report_error(&self, _input: &mut Parser, _position: SourcePosition, _message: &str,
         _url: &ServoUrl) {
     }
-
-     fn clone(&self) -> Box<ParseErrorReporter + Send + Sync> {
-        Box::new(CSSErrorReporterTest)
-     }
 }
 
 fn test_media_rule<F>(css: &str, callback: F)
@@ -34,7 +30,7 @@ fn test_media_rule<F>(css: &str, callback: F)
     let css_str = css.to_owned();
     let stylesheet = Stylesheet::from_str(
         css, url, Origin::Author, Default::default(),
-        None, Box::new(CSSErrorReporterTest),
+        None, &CSSErrorReporterTest,
         ParserContextExtraData::default());
     let mut rule_count = 0;
     media_queries(&stylesheet.rules.read().0, &mut |mq| {
@@ -61,7 +57,7 @@ fn media_query_test(device: &Device, css: &str, expected_rule_count: usize) {
     let url = ServoUrl::parse("http://localhost").unwrap();
     let ss = Stylesheet::from_str(
         css, url, Origin::Author, Default::default(),
-        None, Box::new(CSSErrorReporterTest),
+        None, &CSSErrorReporterTest,
         ParserContextExtraData::default());
     let mut rule_count = 0;
     ss.effective_style_rules(device, |_| rule_count += 1);

tests/unit/style/parsing/background.rs

@@ -15,7 +15,8 @@ use style::stylesheets::Origin;
 #[test]
 fn background_shorthand_should_parse_all_available_properties_when_specified() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("url(\"http://servo/test.png\") top center / 200px 200px repeat-x fixed padding-box \
         content-box red");
     let result = background::parse_value(&context, &mut parser).unwrap();
@@ -34,7 +35,8 @@ fn background_shorthand_should_parse_all_available_properties_when_specified() {
 #[test]
 fn background_shorthand_should_parse_when_some_fields_set() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("14px 40px repeat-y");
     let result = background::parse_value(&context, &mut parser).unwrap();
 
@@ -64,7 +66,8 @@ fn background_shorthand_should_parse_when_some_fields_set() {
 #[test]
 fn background_shorthand_should_parse_comma_separated_declarations() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("url(\"http://servo/test.png\") top left no-repeat, url(\"http://servo/test.png\") \
         center / 100% 100% no-repeat, white");
     let result = background::parse_value(&context, &mut parser).unwrap();
@@ -85,7 +88,8 @@ fn background_shorthand_should_parse_comma_separated_declarations() {
 #[test]
 fn background_shorthand_should_parse_position_and_size_correctly() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("7px 4px");
     let result = background::parse_value(&context, &mut parser).unwrap();
 
@@ -109,7 +113,8 @@ fn background_shorthand_should_parse_position_and_size_correctly() {
 #[test]
 fn background_shorthand_should_parse_origin_and_clip_correctly() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("padding-box content-box");
     let result = background::parse_value(&context, &mut parser).unwrap();
 

tests/unit/style/parsing/border.rs

@@ -15,7 +15,8 @@ use style_traits::ToCss;
 #[test]
 fn border_image_shorthand_should_parse_when_all_properties_specified() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("linear-gradient(red, blue) 30 30% 45 fill / 20px 40px / 10px \
                                  round stretch");
     let result = border_image::parse_value(&context, &mut parser).unwrap();
@@ -31,7 +32,8 @@ fn border_image_shorthand_should_parse_when_all_properties_specified() {
 #[test]
 fn border_image_shorthand_should_parse_without_width() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("linear-gradient(red, blue) 30 30% 45 fill / / 10px round stretch");
     let result = border_image::parse_value(&context, &mut parser).unwrap();
 
@@ -46,7 +48,8 @@ fn border_image_shorthand_should_parse_without_width() {
 #[test]
 fn border_image_shorthand_should_parse_without_outset() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("linear-gradient(red, blue) 30 30% 45 fill / 20px 40px round");
     let result = border_image::parse_value(&context, &mut parser).unwrap();
 
@@ -61,7 +64,8 @@ fn border_image_shorthand_should_parse_without_outset() {
 #[test]
 fn border_image_shorthand_should_parse_without_width_or_outset() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("linear-gradient(red, blue) 30 30% 45 fill round");
     let result = border_image::parse_value(&context, &mut parser).unwrap();
 
@@ -76,7 +80,8 @@ fn border_image_shorthand_should_parse_without_width_or_outset() {
 #[test]
 fn border_image_shorthand_should_parse_with_just_source() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("linear-gradient(red, blue)");
     let result = border_image::parse_value(&context, &mut parser).unwrap();
 
@@ -91,7 +96,8 @@ fn border_image_shorthand_should_parse_with_just_source() {
 #[test]
 fn border_image_outset_should_error_on_negative_length() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("-1em");
     let result = border_image_outset::parse(&context, &mut parser);
     assert_eq!(result, Err(()));
@@ -100,7 +106,8 @@ fn border_image_outset_should_error_on_negative_length() {
 #[test]
 fn border_image_outset_should_error_on_negative_number() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("-15");
     let result = border_image_outset::parse(&context, &mut parser);
     assert_eq!(result, Err(()));
@@ -109,7 +116,8 @@ fn border_image_outset_should_error_on_negative_number() {
 #[test]
 fn border_image_outset_should_return_number_on_plain_zero() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("0");
     let result = border_image_outset::parse(&context, &mut parser);
     assert_eq!(result.unwrap(), parse_longhand!(border_image_outset, "0"));
@@ -118,7 +126,8 @@ fn border_image_outset_should_return_number_on_plain_zero() {
 #[test]
 fn border_image_outset_should_return_length_on_length_zero() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("0em");
     let result = border_image_outset::parse(&context, &mut parser);
     assert_eq!(result.unwrap(), parse_longhand!(border_image_outset, "0em"));

tests/unit/style/parsing/column.rs

@@ -19,7 +19,8 @@ fn test_column_width() {
     assert_roundtrip_with_context!(column_width::parse, "0.3vw");
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let mut negative = Parser::new("-6px");
     assert!(column_width::parse(&context, &mut negative).is_err());
@@ -35,7 +36,8 @@ fn test_column_gap() {
     assert_roundtrip_with_context!(column_gap::parse, "0.3vw");
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let mut negative = Parser::new("-6px");
     assert!(column_gap::parse(&context, &mut negative).is_err());

tests/unit/style/parsing/effects.rs

@@ -38,7 +38,8 @@ fn test_clip() {
 #[test]
 fn test_longhands_parse_origin() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let mut parser = Parser::new("1px some-rubbish");
     let parsed = longhands::parse_origin(&context, &mut parser);

tests/unit/style/parsing/font.rs

@@ -53,7 +53,8 @@ fn font_feature_settings_should_parse_properly() {
 #[test]
 fn font_feature_settings_should_throw_on_bad_input() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let mut empty = Parser::new("");
     assert!(font_feature_settings::parse(&context, &mut empty).is_err());
@@ -103,7 +104,8 @@ fn font_weight_keyword_should_preserve_keyword() {
     use style::properties::longhands::font_weight::SpecifiedValue;
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("normal");
     let result = font_weight::parse(&context, &mut parser);
     assert_eq!(result.unwrap(), SpecifiedValue::Normal);

tests/unit/style/parsing/inherited_text.rs

@@ -111,7 +111,8 @@ fn webkit_text_stroke_shorthand_should_parse_properly() {
     use style::properties::shorthands::_webkit_text_stroke;
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let mut parser = Parser::new("thin red");
     let result = _webkit_text_stroke::parse_value(&context, &mut parser).unwrap();
@@ -132,7 +133,8 @@ fn line_height_should_return_number_on_plain_zero() {
     use style::properties::longhands::line_height;
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("0");
     let result = line_height::parse(&context, &mut parser);
     assert_eq!(result.unwrap(), parse_longhand!(line_height, "0"));
@@ -145,7 +147,8 @@ fn line_height_should_return_length_on_length_zero() {
     use style::properties::longhands::line_height;
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("0px");
     let result = line_height::parse(&context, &mut parser);
     assert_eq!(result.unwrap(), parse_longhand!(line_height, "0px"));

tests/unit/style/parsing/mask.rs

@@ -14,7 +14,8 @@ use style::stylesheets::Origin;
 #[test]
 fn mask_shorthand_should_parse_all_available_properties_when_specified() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("url(\"http://servo/test.png\") luminance 7px 4px / 70px 50px \
                                  repeat-x padding-box border-box subtract");
     let result = mask::parse_value(&context, &mut parser).unwrap();
@@ -33,7 +34,8 @@ fn mask_shorthand_should_parse_all_available_properties_when_specified() {
 #[test]
 fn mask_shorthand_should_parse_when_some_fields_set() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("14px 40px repeat-y");
     let result = mask::parse_value(&context, &mut parser).unwrap();
 
@@ -62,7 +64,8 @@ fn mask_shorthand_should_parse_when_some_fields_set() {
 #[test]
 fn mask_shorthand_should_parse_position_and_size_correctly() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("7px 4px");
     let result = mask::parse_value(&context, &mut parser).unwrap();
 
@@ -86,7 +89,8 @@ fn mask_shorthand_should_parse_position_and_size_correctly() {
 #[test]
 fn mask_shorthand_should_parse_origin_and_clip_correctly() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("padding-box content-box");
     let result = mask::parse_value(&context, &mut parser).unwrap();
 
@@ -109,7 +113,8 @@ fn mask_shorthand_should_parse_origin_and_clip_correctly() {
 #[test]
 fn mask_shorthand_should_parse_mode_everywhere() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new("luminance 7px 4px repeat-x padding-box");
     assert!(mask::parse_value(&context, &mut parser).is_ok());
 

tests/unit/style/parsing/mod.rs

@@ -11,7 +11,8 @@ use style::stylesheets::Origin;
 
 fn parse<T, F: Fn(&ParserContext, &mut Parser) -> Result<T, ()>>(f: F, s: &str) -> Result<T, ()> {
     let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new(s);
     f(&context, &mut parser)
 }
@@ -24,7 +25,8 @@ macro_rules! assert_roundtrip_with_context {
     };
     ($fun:expr,$input:expr, $output:expr) => {
         let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-        let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+        let reporter = CSSErrorReporterTest;
+        let context = ParserContext::new(Origin::Author, &url, &reporter);
         let mut parser = Parser::new($input);
         let parsed = $fun(&context, &mut parser)
                      .expect(&format!("Failed to parse {}", $input));
@@ -61,7 +63,8 @@ macro_rules! assert_roundtrip {
 macro_rules! assert_parser_exhausted {
     ($name:ident, $string:expr, $should_exhausted:expr) => {{
         let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-        let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+        let reporter = CSSErrorReporterTest;
+        let context = ParserContext::new(Origin::Author, &url, &reporter);
         let mut parser = Parser::new($string);
         let parsed = $name::parse(&context, &mut parser);
         assert_eq!(parsed.is_ok(), true);
@@ -72,7 +75,8 @@ macro_rules! assert_parser_exhausted {
 macro_rules! parse_longhand {
     ($name:ident, $s:expr) => {{
         let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-        let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+        let reporter = CSSErrorReporterTest;
+        let context = ParserContext::new(Origin::Author, &url, &reporter);
         $name::parse(&context, &mut Parser::new($s)).unwrap()
     }};
 }

tests/unit/style/parsing/outline.rs

@@ -28,7 +28,8 @@ fn test_outline_style() {
         // except that 'hidden' is not a legal outline style.
 
         let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-        let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+        let reporter = CSSErrorReporterTest;
+        let context = ParserContext::new(Origin::Author, &url, &reporter);
         let mut parser = Parser::new(r#"hidden"#);
         let parsed = outline_style::parse(&context, &mut parser);
         assert!(parsed.is_err());

tests/unit/style/parsing/ui.rs

@@ -27,7 +27,8 @@ fn test_moz_user_select() {
     assert_roundtrip_with_context!(_moz_user_select::parse, "-moz-text");
 
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let mut negative = Parser::new("potato");
     assert!(_moz_user_select::parse(&context, &mut negative).is_err());

tests/unit/style/properties/background.rs

@@ -11,7 +11,8 @@ use style::stylesheets::Origin;
 #[test]
 fn background_size_should_reject_negative_values() {
     let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     let parse_result = background_size::parse(&context, &mut Parser::new("-40% -40%"));
 

tests/unit/style/properties/serialization.rs

@@ -21,7 +21,8 @@ use stylesheets::block_from;
 
 fn parse_declaration_block(css_properties: &str) -> PropertyDeclarationBlock {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
     let mut parser = Parser::new(css_properties);
     parse_property_declaration_list(&context, &mut parser)
 }
@@ -963,7 +964,8 @@ mod shorthand_serialization {
 
             let mut s = String::new();
             let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-            let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+            let reporter = CSSErrorReporterTest;
+            let context = ParserContext::new(Origin::Author, &url, &reporter);
 
             let parsed = transform::parse(&context, &mut Parser::new("none")).unwrap();
             let try_serialize = parsed.to_css(&mut s);
@@ -986,7 +988,8 @@ mod shorthand_serialization {
 
             let mut s = String::new();
             let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
-            let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+            let reporter = CSSErrorReporterTest;
+            let context = ParserContext::new(Origin::Author, &url, &reporter);
 
             let parsed = quotes::parse(&context, &mut Parser::new("none")).unwrap();
             let try_serialize = parsed.to_css(&mut s);

tests/unit/style/rule_tree/bench.rs

@@ -21,10 +21,6 @@ impl ParseErrorReporter for ErrorringErrorReporter {
         url: &ServoUrl) {
         panic!("CSS error: {}\t\n{:?} {}", url.as_str(), position, message);
     }
-
-    fn clone(&self) -> Box<ParseErrorReporter + Send + Sync> {
-        Box::new(ErrorringErrorReporter)
-    }
 }
 
 struct AutoGCRuleTree<'a>(&'a RuleTree);
@@ -49,7 +45,7 @@ fn parse_rules(css: &str) -> Vec<(StyleSource, CascadeLevel)> {
                                      media_queries: vec![],
                                  },
                                  None,
-                                 Box::new(ErrorringErrorReporter),
+                                 &ErrorringErrorReporter,
                                  ParserContextExtraData {});
     let rules = s.rules.read();
     rules.0.iter().filter_map(|rule| {

tests/unit/style/stylesheets.rs

@@ -63,7 +63,7 @@ fn test_parse_stylesheet() {
     let url = ServoUrl::parse("about::test").unwrap();
     let stylesheet = Stylesheet::from_str(css, url.clone(), Origin::UserAgent, Default::default(),
                                           None,
-                                          Box::new(CSSErrorReporterTest),
+                                          &CSSErrorReporterTest,
                                           ParserContextExtraData::default());
     let mut namespaces = Namespaces::default();
     namespaces.default = Some(ns!(html));
@@ -289,13 +289,15 @@ impl CSSInvalidErrorReporterTest {
 }
 
 impl ParseErrorReporter for CSSInvalidErrorReporterTest {
-    fn report_error(&self, input: &mut CssParser, position: SourcePosition, message: &str,
+    fn report_error(&self,
+                    input: &mut CssParser,
+                    position: SourcePosition,
+                    message: &str,
                     url: &ServoUrl) {
 
         let location = input.source_location(position);
 
-        let errors = self.errors.clone();
+        let mut errors = self.errors.lock().unwrap();
-        let mut errors = errors.lock().unwrap();
 
         errors.push(
             CSSError{
@@ -306,14 +308,6 @@ impl ParseErrorReporter for CSSInvalidErrorReporterTest {
             }
         );
     }
-
-    fn clone(&self) -> Box<ParseErrorReporter + Send + Sync> {
-        return Box::new(
-            CSSInvalidErrorReporterTest{
-                errors: self.errors.clone()
-            }
-        );
-    }
 }
 
 
@@ -327,13 +321,13 @@ fn test_report_error_stylesheet() {
     }
     ";
     let url = ServoUrl::parse("about::test").unwrap();
-    let error_reporter = Box::new(CSSInvalidErrorReporterTest::new());
+    let error_reporter = CSSInvalidErrorReporterTest::new();
 
     let errors = error_reporter.errors.clone();
 
     Stylesheet::from_str(css, url.clone(), Origin::UserAgent, Default::default(),
                          None,
-                         error_reporter,
+                         &error_reporter,
                          ParserContextExtraData::default());
 
     let mut errors = errors.lock().unwrap();

tests/unit/style/viewport.rs

@@ -7,7 +7,6 @@ use euclid::size::TypedSize2D;
 use media_queries::CSSErrorReporterTest;
 use servo_config::prefs::{PREFS, PrefValue};
 use servo_url::ServoUrl;
-use style::error_reporting::ParseErrorReporter;
 use style::media_queries::{Device, MediaType};
 use style::parser::{ParserContext, ParserContextExtraData};
 use style::stylesheets::{Stylesheet, Origin};
@@ -26,7 +25,7 @@ macro_rules! stylesheet {
             Origin::$origin,
             Default::default(),
             None,
-            $error_reporter,
+            &$error_reporter,
             ParserContextExtraData::default()
         ))
     }
@@ -38,7 +37,7 @@ fn test_viewport_rule<F>(css: &str,
     where F: Fn(&Vec<ViewportDescriptorDeclaration>, &str)
 {
     PREFS.set("layout.viewport.enabled", PrefValue::Boolean(true));
-    let stylesheet = stylesheet!(css, Author, Box::new(CSSErrorReporterTest));
+    let stylesheet = stylesheet!(css, Author, CSSErrorReporterTest);
     let mut rule_count = 0;
     stylesheet.effective_viewport_rules(&device, |rule| {
         rule_count += 1;
@@ -253,9 +252,9 @@ fn multiple_stylesheets_cascading() {
     let device = Device::new(MediaType::Screen, TypedSize2D::new(800., 600.));
     let error_reporter = CSSErrorReporterTest;
     let stylesheets = vec![
-        stylesheet!("@viewport { min-width: 100px; min-height: 100px; zoom: 1; }", UserAgent, error_reporter.clone()),
+        stylesheet!("@viewport { min-width: 100px; min-height: 100px; zoom: 1; }", UserAgent, error_reporter),
-        stylesheet!("@viewport { min-width: 200px; min-height: 200px; }", User, error_reporter.clone()),
+        stylesheet!("@viewport { min-width: 200px; min-height: 200px; }", User, error_reporter),
-        stylesheet!("@viewport { min-width: 300px; }", Author, error_reporter.clone())];
+        stylesheet!("@viewport { min-width: 300px; }", Author, error_reporter)];
 
     let declarations = Cascade::from_stylesheets(&stylesheets, &device).finish();
     assert_decl_len!(declarations == 3);
@@ -264,11 +263,11 @@ fn multiple_stylesheets_cascading() {
     assert_decl_eq!(&declarations[2], Author, MinWidth: viewport_length!(300., px));
 
     let stylesheets = vec![
-        stylesheet!("@viewport { min-width: 100px !important; }", UserAgent, error_reporter.clone()),
+        stylesheet!("@viewport { min-width: 100px !important; }", UserAgent, error_reporter),
         stylesheet!("@viewport { min-width: 200px !important; min-height: 200px !important; }",
-        User, error_reporter.clone()),
+        User, error_reporter),
         stylesheet!("@viewport { min-width: 300px !important; min-height: 300px !important; zoom: 3 !important; }",
-        Author, error_reporter.clone())];
+        Author, error_reporter)];
     let declarations = Cascade::from_stylesheets(&stylesheets, &device).finish();
     assert_decl_len!(declarations == 3);
     assert_decl_eq!(&declarations[0], UserAgent, MinWidth: viewport_length!(100., px), !important);
@@ -279,7 +278,8 @@ fn multiple_stylesheets_cascading() {
 #[test]
 fn constrain_viewport() {
     let url = ServoUrl::parse("http://localhost").unwrap();
-    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter);
 
     macro_rules! from_css {
         ($css:expr) => {