Implement basics of link preloading

These changes allow a minimal set of checks for font-src
CSP checks to pass.

Part of servo#4577
Part of servo#35035

Signed-off-by: Tim van der Lippe <[email protected]>

Author: TimvdLippe

components/script/dom/element.rs

@@ -13,7 +13,7 @@ use std::str::FromStr;
 use std::{fmt, mem};
 
 use content_security_policy as csp;
-use cssparser::match_ignore_ascii_case;
+use cssparser::{Parser as CssParser, ParserInput as CssParserInput, match_ignore_ascii_case};
 use devtools_traits::AttrInfo;
 use dom_struct::dom_struct;
 use embedder_traits::InputMethodType;
@@ -36,6 +36,8 @@ use style::applicable_declarations::ApplicableDeclarationBlock;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto};
 use style::context::QuirksMode;
 use style::invalidation::element::restyle_hints::RestyleHint;
+use style::media_queries::MediaList;
+use style::parser::ParserContext as CssParserContext;
 use style::properties::longhands::{
     self, background_image, border_spacing, font_family, font_size,
 };
@@ -50,13 +52,14 @@ use style::selector_parser::{
 };
 use style::shared_lock::{Locked, SharedRwLock};
 use style::stylesheets::layer_rule::LayerOrder;
-use style::stylesheets::{CssRuleType, UrlExtraData};
+use style::stylesheets::{CssRuleType, Origin as CssOrigin, UrlExtraData};
 use style::values::computed::Overflow;
 use style::values::generics::NonNegative;
 use style::values::generics::position::PreferredRatio;
 use style::values::generics::ratio::Ratio;
 use style::values::{AtomIdent, AtomString, CSSFloat, computed, specified};
 use style::{ArcSlice, CaseSensitivityExt, dom_apis, thread_state};
+use style_traits::ParsingMode as CssParsingMode;
 use stylo_atoms::Atom;
 use stylo_dom::ElementState;
 use xml5ever::serialize::TraversalScope::{
@@ -781,6 +784,33 @@ impl Element {
             .registered_intersection_observers
             .retain(|reg_obs| *reg_obs.observer != *observer)
     }
+
+    /// <https://html.spec.whatwg.org/multipage/#matches-the-environment>
+    pub(crate) fn matches_environment(&self, media_query: &str) -> bool {
+        let document = self.owner_document();
+        let quirks_mode = document.quirks_mode();
+        let document_url_data = UrlExtraData(document.url().get_arc());
+        // FIXME(emilio): This should do the same that we do for other media
+        // lists regarding the rule type and such, though it doesn't really
+        // matter right now...
+        //
+        // Also, ParsingMode::all() is wrong, and should be DEFAULT.
+        let context = CssParserContext::new(
+            CssOrigin::Author,
+            &document_url_data,
+            Some(CssRuleType::Style),
+            CssParsingMode::all(),
+            quirks_mode,
+            /* namespaces = */ Default::default(),
+            None,
+            None,
+        );
+        let mut parser_input = CssParserInput::new(media_query);
+        let mut parser = CssParser::new(&mut parser_input);
+        let media_list = MediaList::parse(&context, &mut parser);
+        let result = media_list.evaluate(document.window().layout().device(), quirks_mode);
+        result
+    }
 }
 
 /// <https://dom.spec.whatwg.org/#valid-shadow-host-name>

components/script/dom/htmlimageelement.rs

@@ -34,9 +34,8 @@ use servo_url::ServoUrl;
 use servo_url::origin::MutableOrigin;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto, parse_integer, parse_length};
 use style::context::QuirksMode;
-use style::media_queries::MediaList;
 use style::parser::ParserContext;
-use style::stylesheets::{CssRuleType, Origin, UrlExtraData};
+use style::stylesheets::{CssRuleType, Origin};
 use style::values::specified::AbsoluteLength;
 use style::values::specified::length::{Length, NoCalcLength};
 use style::values::specified::source_size_list::SourceSizeList;
@@ -675,7 +674,7 @@ impl HTMLImageElement {
 
             // Step 4.6
             if let Some(x) = element.get_attribute(&ns!(), &local_name!("media")) {
-                if !self.matches_environment(x.value().to_string()) {
+                if !elem.matches_environment(&x.value()) {
                     continue;
                 }
             }
@@ -719,33 +718,6 @@ impl HTMLImageElement {
         result
     }
 
-    /// <https://html.spec.whatwg.org/multipage/#matches-the-environment>
-    fn matches_environment(&self, media_query: String) -> bool {
-        let document = self.owner_document();
-        let quirks_mode = document.quirks_mode();
-        let document_url_data = UrlExtraData(document.url().get_arc());
-        // FIXME(emilio): This should do the same that we do for other media
-        // lists regarding the rule type and such, though it doesn't really
-        // matter right now...
-        //
-        // Also, ParsingMode::all() is wrong, and should be DEFAULT.
-        let context = ParserContext::new(
-            Origin::Author,
-            &document_url_data,
-            Some(CssRuleType::Style),
-            ParsingMode::all(),
-            quirks_mode,
-            /* namespaces = */ Default::default(),
-            None,
-            None,
-        );
-        let mut parserInput = ParserInput::new(&media_query);
-        let mut parser = Parser::new(&mut parserInput);
-        let media_list = MediaList::parse(&context, &mut parser);
-        let result = media_list.evaluate(document.window().layout().device(), quirks_mode);
-        result
-    }
-
     /// <https://html.spec.whatwg.org/multipage/#normalise-the-source-densities>
     fn normalise_source_densities(&self, source_set: &mut SourceSet, width: Option<Length>) {
         // Step 1