style: Move the error reporter into ParserContext.

Summary:
This should make it easier to report errors, and also reduce codesize.

The reason this was so generic is that error reporting was unconditionally
enabled and was super-hot, but now that's no longer the case after bug 1452143,
so we can afford the virtual call in the "error reporting enabled" case.

This opens the possibility of simplifying a lot the error setup as well, though
this patch doesn't do it.

Test Plan: No behavior change, so no new tests.

Reviewers: xidorn

Bug #: 1469957

Differential Revision: https://phabricator.services.mozilla.com/D1734

MozReview-Commit-ID: F3wTdhX9MB5

components/style/stylesheets/stylesheet.rs

@@ -13,7 +13,7 @@ use invalidation::media_queries::{MediaListKey, ToMediaListKey};
 use malloc_size_of::{MallocSizeOfOps, MallocUnconditionalShallowSizeOf};
 use media_queries::{Device, MediaList};
 use parking_lot::RwLock;
-use parser::{ParserContext, ParserErrorContext};
+use parser::ParserContext;
 use servo_arc::Arc;
 use shared_lock::{DeepCloneParams, DeepCloneWithLock, Locked, SharedRwLock, SharedRwLockReadGuard};
 use std::mem;
@@ -69,13 +69,13 @@ pub struct StylesheetContents {
 impl StylesheetContents {
     /// Parse a given CSS string, with a given url-data, origin, and
     /// quirks mode.
-    pub fn from_str<R: ParseErrorReporter>(
+    pub fn from_str(
         css: &str,
         url_data: UrlExtraData,
         origin: Origin,
         shared_lock: &SharedRwLock,
         stylesheet_loader: Option<&StylesheetLoader>,
-        error_reporter: &R,
+        error_reporter: Option<&ParseErrorReporter>,
         quirks_mode: QuirksMode,
         line_number_offset: u32,
     ) -> Self {
@@ -306,18 +306,16 @@ impl StylesheetInDocument for DocumentStyleSheet {
 
 impl Stylesheet {
     /// Updates an empty stylesheet from a given string of text.
-    pub fn update_from_str<R>(
+    pub fn update_from_str(
         existing: &Stylesheet,
         css: &str,
         url_data: UrlExtraData,
         stylesheet_loader: Option<&StylesheetLoader>,
-        error_reporter: &R,
+        error_reporter: Option<&ParseErrorReporter>,
         line_number_offset: u32,
-    ) where
-        R: ParseErrorReporter,
-    {
+    ) {
         let namespaces = RwLock::new(Namespaces::default());
-        let (rules, source_map_url, source_url) = Stylesheet::parse_rules(
+        let (rules, source_map_url, source_url) = Self::parse_rules(
             css,
             &url_data,
             existing.contents.origin,
@@ -342,14 +340,14 @@ impl Stylesheet {
         *existing.contents.source_url.write() = source_url;
     }
 
-    fn parse_rules<R: ParseErrorReporter>(
+    fn parse_rules(
         css: &str,
         url_data: &UrlExtraData,
         origin: Origin,
         namespaces: &mut Namespaces,
         shared_lock: &SharedRwLock,
         stylesheet_loader: Option<&StylesheetLoader>,
-        error_reporter: &R,
+        error_reporter: Option<&ParseErrorReporter>,
         quirks_mode: QuirksMode,
         line_number_offset: u32,
     ) -> (Vec<CssRule>, Option<String>, Option<String>) {
@@ -357,16 +355,20 @@ impl Stylesheet {
         let mut input = ParserInput::new_with_line_number_offset(css, line_number_offset);
         let mut input = Parser::new(&mut input);
 
-        let context = ParserContext::new(origin, url_data, None, ParsingMode::DEFAULT, quirks_mode);
-
-        let error_context = ParserErrorContext { error_reporter };
+        let context = ParserContext::new(
+            origin,
+            url_data,
+            None,
+            ParsingMode::DEFAULT,
+            quirks_mode,
+            error_reporter,
+        );
 
         let rule_parser = TopLevelRuleParser {
             stylesheet_origin: origin,
             shared_lock,
             loader: stylesheet_loader,
             context,
-            error_context,
             state: State::Start,
             dom_error: None,
             insert_rule_context: None,
@@ -390,7 +392,6 @@ impl Stylesheet {
                         let location = error.location;
                         let error = ContextualParseError::InvalidRule(slice, error);
                         iter.parser.context.log_css_error(
-                            &iter.parser.error_context,
                             location,
                             error,
                         );
@@ -409,17 +410,17 @@ impl Stylesheet {
     ///
     /// Effectively creates a new stylesheet and forwards the hard work to
     /// `Stylesheet::update_from_str`.
-    pub fn from_str<R: ParseErrorReporter>(
+    pub fn from_str(
         css: &str,
         url_data: UrlExtraData,
         origin: Origin,
         media: Arc<Locked<MediaList>>,
         shared_lock: SharedRwLock,
         stylesheet_loader: Option<&StylesheetLoader>,
-        error_reporter: &R,
+        error_reporter: Option<&ParseErrorReporter>,
         quirks_mode: QuirksMode,
         line_number_offset: u32,
-    ) -> Stylesheet {
+    ) -> Self {
         let contents = StylesheetContents::from_str(
             css,
             url_data,