Auto merge of #20718 - paulrouget:res2, r=emilio

Automatically provide a resource reader for tests

Fix #20710

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- [ ] `./mach build-geckolib` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #20710 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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tests/unit/style/Cargo.toml

@@ -13,7 +13,6 @@ doctest = false
 byteorder = "1.0"
 app_units = "0.6"
 cssparser = "0.23.0"
-embedder_traits = {path = "../../../components/embedder_traits"}
 euclid = "0.17"
 html5ever = "0.22"
 parking_lot = "0.5"

tests/unit/style/lib.rs

@@ -7,7 +7,6 @@
 
 extern crate app_units;
 extern crate cssparser;
-extern crate embedder_traits;
 extern crate euclid;
 #[macro_use] extern crate html5ever;
 extern crate parking_lot;

tests/unit/style/stylesheets.rs

@@ -3,7 +3,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use cssparser::{self, SourceLocation};
-use embedder_traits::resources::register_resources_for_tests;
 use html5ever::{Namespace as NsAtom};
 use media_queries::CSSErrorReporterTest;
 use parking_lot::RwLock;
@@ -322,7 +321,6 @@ impl ParseErrorReporter for TestingErrorReporter {
 
 #[test]
 fn test_report_error_stylesheet() {
-    register_resources_for_tests();
     PREFS.set("layout.viewport.enabled", PrefValue::Boolean(true));
     let css = r"
     div {